17 Forms
Contents
- Introduction to forms
- Controls
- The FORM element
- The INPUT element
- The BUTTON element
- The SELECT, OPTGROUP, and OPTION elements
- The TEXTAREA element
- The ISINDEX element
- Labels
- Adding structure to forms: the FIELDSET and LEGEND elements
- Giving focus to an element
- Disabled and read-only controls
- Form submission
17.1 Introduction to forms
An HTML form is a section of a document containing normal content, markup, special elements called controls (checkboxes, radio buttons, menus, etc.), and labels on those controls. Users generally "complete" a form by modifying its controls (entering text selecting menu items, etc.), before submitting the form to an agent for processing (e.g., to a Web server, to a mail server, etc.)
Here's a simple form that includes labels, radio buttons, and push buttons (reset the form or submit it):
<FORM action="http://somesite.com/prog/adduser" method="post">
<P>
<LABEL for="firstname">First name: </LABEL>
<INPUT type="text" id="firstname"><BR>
<LABEL for="lastname">Last name: </LABEL>
<INPUT type="text" id="lastname"><BR>
<LABEL for="email">email: </LABEL>
<INPUT type="text" id="email"><BR>
<INPUT type="radio" name="sex" value="Male"> Male<BR>
<INPUT type="radio" name="sex" value="Female"> Female<BR>
<INPUT type="submit" value="Send"> <INPUT type="reset">
</P>
</FORM>
Note. This specification includes more detailed information about forms in the subsections on form display issues.
17.2 Controls
Users interact with forms through named controls.
A control's "control name" is given by its name attribute. The scope of the name attribute for a control within a FORM element is the FORM element.
Each control has both an initial value and a current value, both of which are character strings. Please consult the definition of each control for information about initial values and possible constraints on values imposed by the control. In general, a control's "initial value" may be specified with the control element's value attribute. However, the initial value of a TEXTAREA element is given by its contents, and the initial value of an OBJECT element in a form is determined by the object implementation (i.e., it lies outside the scope of this specification).
The control's "current value" is first set to the initial value. Thereafter, the control's current value may be modified through user interaction and scripts.
A control's initial value does not change. Thus, when a form is reset, each control's current value is reset to its initial value. If a control does not have an initial value, the effect of a form reset on that control is undefined.
When a form is submitted for processing, some controls have their name paired with their current value and these pairs are submitted with the form. Those controls which name/value pairs are submitted are called successful controls.
17.2.1 Control types
HTML defines the following control types:
- buttons
- Authors may create three types of buttons:
submit buttons: When activated, a
submit button submits a form. A form may
contain more than one submit button.
| reset buttons: When activated, a reset
button resets all controls to their initial
values.
|
push buttons:
Push buttons have no default behavior. Each push button may have client-side scripts associated with the
element's event attributes. When an
event occurs (e.g., the user presses the button, releases it, etc.),
the associated script is triggered.
| Authors should specify the scripting language of a push button script through a default script declaration (with the META element). |
Authors create buttons with the BUTTON element or the INPUT element. Please consult the definitions of these elements for details about specifying different button types.
Note. Authors should note that the BUTTON element offers richer rendering capabilities than the INPUT element.
When a form is submitted, only "on" checkbox controls can become successful. Several checkboxes in a form may share the same control name. Thus, for example, checkboxes allow users to select several values for the same property. The INPUT element is used to create a checkbox control.
The elements used to create controls generally appear inside a FORM element, but may also appear outside of a FORM element declaration when they are used to build user interfaces. This is discussed in the section on intrinsic events. Note that controls outside a form cannot be successful controls.
17.3 The FORM element
<!ELEMENT FORM - - (%block;|SCRIPT)+ -(FORM) -- interactive form --> <!ATTLIST FORM %attrs; -- %coreattrs, %i18n, %events -- action %URI; #REQUIRED -- server-side form handler -- method (GET|POST) GET -- HTTP method used to submit the form-- enctype %ContentType; "application/x-www-form-urlencoded" onsubmit %Script; #IMPLIED -- the form was submitted -- onreset %Script; #IMPLIED -- the form was reset -- accept-charset %Charsets; #IMPLIED -- list of supported charsets -- >
Start tag: required, End tag: required
Attribute definitions
- action = uri [CT]
- This attribute specifies a form processing agent. For example, the value might be a HTTP URI (to submit the form to a program) or a mailto URI (to email the form).
- method = get|post [CI]
- This attribute specifies which HTTP method will be used to submit the form data set. Possible (case-insensitive) values are "get" (the default) and "post". See the section on form submission for usage information.
- enctype = content-type [CI]
- This attribute specifies the content type used to submit the form to the server (when the value of method is "post"). The default value for this attribute is "application/x-www-form-urlencoded". The value "multipart/form-data" should be used in combination with the INPUT element, type="file".
- accept-charset = charset list [CI]
- This attribute specifies the list of character encodings for
input data that must be accepted by the server processing this
form. The value is a space- and/or comma-delimited list of charset values. The server must
interpret this list as an exclusive-or list, i.e., the server must be
able to accept any single character encoding per entity received.
The default value for this attribute is the reserved string "UNKNOWN". User agents may interpret this value as the character encoding that was used to transmit the document containing this FORM element.
- accept = content-type-list [CI]
- This attribute specifies a comma-separated list of content types that a server processing this form will handle correctly. User agents may use this information to filter out non-conforming files when prompting a user to select files to be sent to the server (cf. the INPUT element when type="file").
Attributes defined elsewhere
The FORM element acts as a container for controls. It specifies:
The layout of the form (given by the contents of the element).
| The program that will handle the completed and submitted form
(the action attribute). The receiving
program must be able to parse name/value pairs in order to
make use of them.
| The method by which user data will be sent to the server
(the method attribute).
| A character encoding that must be accepted by the server in order
to handle this form (the accept-charset
attribute). User agents may advise the user of the value of the accept-charset attribute and/or restrict the
user's ability to enter unrecognized characters.
| |
A form can contain text and markup (paragraphs, lists, etc.) in addition to form controls.
The following example shows a form that is to be processed by the "adduser" program when submitted. The form will be sent to the program using the HTTP "post" method.
<FORM action="http://somesite.com/prog/adduser" method="post"> ...form contents... </FORM>
The next example shows how to send a submitted form to an email address:
<FORM action="mailto:[email protected]" method="post"> ...form contents... </FORM>
Please consult the section on form submission for information about how user agents must prepare form data for servers and how user agents should handle expected responses.
Note. Further discussion on the behavior of servers that receive form data is beyond the scope of this specification.
17.4 The INPUT element
<!ENTITY % InputType
"(TEXT | PASSWORD | CHECKBOX |
RADIO | SUBMIT | RESET |
FILE | HIDDEN | IMAGE | BUTTON)"
>
<!-- attribute name required for all but submit & reset -->
<!ELEMENT INPUT - O EMPTY -- form control -->
<!ATTLIST INPUT
%attrs; -- %coreattrs, %i18n, %events --
type %InputType; TEXT -- what kind of widget is needed --
name CDATA #IMPLIED -- submit as part of form --
value CDATA #IMPLIED -- required for radio and checkboxes --
checked (checked) #IMPLIED -- for radio buttons and check boxes --
disabled (disabled) #IMPLIED -- unavailable in this context --
readonly (readonly) #IMPLIED -- for text and passwd --
size CDATA #IMPLIED -- specific to each type of field --
maxlength NUMBER #IMPLIED -- max chars for text fields --
src %URI; #IMPLIED -- for fields with images --
alt CDATA #IMPLIED -- short description --
usemap %URI; #IMPLIED -- use client-side image map --
tabindex NUMBER #IMPLIED -- position in tabbing order --
accesskey %Character; #IMPLIED -- accessibility key character --
onfocus %Script; #IMPLIED -- the element got the focus --
onblur %Script; #IMPLIED -- the element lost the focus --
onselect %Script; #IMPLIED -- some text was selected --
onchange %Script; #IMPLIED -- the element value was changed --
accept %ContentTypes; #IMPLIED -- list of MIME types for file upload --
>
Start tag: required, End tag: forbidden
Attribute definitions
- type = text|password|checkbox|radio|submit|reset|file|hidden|image|button [CI]
- This attribute specifies the type of control to create. The default value for this attribute is "text".
- name = cdata [CI]
- This attribute assigns the control name.
- value = cdata [CA]
- This attribute specifies the initial value of the control. It is optional except when the type attribute has the value "radio".
- size = cdata [CN]
- This attribute tells the user agent the initial width of the control. The width is given in pixels except when type attribute has the value "text" or "password". In that case, its value refers to the (integer) number of characters.
- maxlength = number [CN]
- When the type attribute has the value "text" or "password", this attribute specifies the maximum number of characters the user may enter. This number may exceed the specified size, in which case the user agent should offer a scrolling mechanism. The default value for this attribute is an unlimited number.
- checked [CI]
- When the type attribute has the value "radio" or "checkbox", this boolean attribute specifies that the button is on. User agents must ignore this attribute for other control types.
- src = uri [CT]
- When the type attribute has the value "image", this attribute specifies the location of the image to be used to decorate the graphical submit button.
Attributes defined elsewhere
17.4.1 Control types created with INPUT
The control type defined by the INPUT element depends on the value of the type attribute:
- text
- Creates a single-line text input control.
- password
-
Like "text", but the input text is rendered in such a way as to
hide the characters (e.g., a series of asterisks). This control type
is often used for sensitive input such as passwords. Note that the current value is the text entered
by the user, not the text rendered by the user agent.
Note. Application designers should note that this mechanism affords only light security protection. Although the password is masked by user agents from casual observers, it is transmitted to the server in clear text, and may be read by anyone with low-level access to the network.
- checkbox
- Creates a checkbox.
- radio
- Creates a radio button.
- submit
- Creates a submit button.
- image
- Creates a graphical submit button.
The value of the src attribute specifies
the URI of the image that will decorate the button. For accessibility
reasons, authors should provide alternate text for
the image via the alt attribute.
When a pointing device is used to click on the image, the form is submitted and the click coordinates passed to the server. The x value is measured in pixels from the left of the image, and the y value in pixels from the top of the image. The submitted data includes name.x=x-value and name.y=y-value where "name" is the value of the name attribute, and x-value and y-value are the x and y coordinate values, respectively.
If the server takes different actions depending on the location clicked, users of non-graphical browsers will be disadvantaged. For this reason, authors should consider alternate approaches:
Use multiple submit buttons (each with its own image) in place of
a single graphical submit button. Authors may use style sheets to
control the positioning of these buttons.
| Use a client-side
image map together with scripting.
| |
17.4.2 Examples of forms containing INPUT controls
The following sample HTML fragment defines a simple form that allows the user to enter a first name, last name, email address, and gender. When the submit button is activated, the form will be sent to the program specified by the action attribute.
<FORM action="http://somesite.com/prog/adduser" method="post">
<P>
First name: <INPUT type="text" name="firstname"><BR>
Last name: <INPUT type="text" name="lastname"><BR>
email: <INPUT type="text" name="email"><BR>
<INPUT type="radio" name="sex" value="Male"> Male<BR>
<INPUT type="radio" name="sex" value="Female"> Female<BR>
<INPUT type="submit" value="Send"> <INPUT type="reset">
</P>
</FORM>
This form might be rendered as follows:
In the section on the LABEL element, we discuss marking up labels such as "First name".
In this next example, the JavaScript function name verify is triggered when the "onclick" event occurs:
<HEAD>
<META http-equiv="Content-Script-Type" content="text/javascript">
</HEAD>
<BODY>
<FORM action="..." method="post">
<P>
<INPUT type="button" value="Click Me" onclick="verify()">
</FORM>
</BODY>
Please consult the section on intrinsic events for more information about scripting and events.
The following example shows how the contents of a user-specified file may be submitted with a form. The user is prompted for his or her name and a list of file names whose contents should be submitted with the form. By specifying the enctype value of "multipart/form-data", each file's contents will be packaged for submission in a separate section of a multipart document.
<FORM action="http://server.dom/cgi/handle"
enctype="multipart/form-data"
method="post">
<P>
What is your name? <INPUT type="text" name="name_of_sender">
What files are you sending? <INPUT type="file" name="name_of_files">
</P>
</FORM>
17.5 The BUTTON element
<!ELEMENT BUTTON - - (%flow;)* -(A|%formctrl;|FORM|FIELDSET) -- push button --> <!ATTLIST BUTTON %attrs; -- %coreattrs, %i18n, %events -- name CDATA #IMPLIED value CDATA #IMPLIED -- sent to server when submitted -- type (button|submit|reset) submit -- for use as form button -- disabled (disabled) #IMPLIED -- unavailable in this context -- tabindex NUMBER #IMPLIED -- position in tabbing order -- accesskey %Character; #IMPLIED -- accessibility key character -- onfocus %Script; #IMPLIED -- the element got the focus -- onblur %Script; #IMPLIED -- the element lost the focus -- >
Start tag: required, End tag: required
Attribute definitions
- name = cdata [CI]
- This attribute assigns the control name.
- value = cdata [CS]
- This attribute assigns the initial value to the button.
- type = submit|button|reset [CI]
- This attribute declares the type of the button. Possible values:
submit: Creates a submit button. This is the default value. reset: Creates a reset button. button: Creates a push button.
Attributes defined elsewhere
Buttons created with the BUTTON element function just like buttons created with the INPUT element, but they offer richer rendering possibilities: the BUTTON element may have content. For example, a BUTTON element that contains an image functions like and may resemble an INPUT element whose type is set to "image", but the BUTTON element type allows content.
Visual user agents may render BUTTON buttons with relief and an up/down motion when clicked, while they may render INPUT buttons as a "flat" images.
The following example expands a previous example, but creates submit and reset buttons with BUTTON instead of INPUT. The buttons contain images by way of the IMG element.
<FORM action="http://somesite.com/prog/adduser" method="post">
<P>
First name: <INPUT type="text" name="firstname"><BR>
Last name: <INPUT type="text" name="lastname"><BR>
email: <INPUT type="text" name="email"><BR>
<INPUT type="radio" name="sex" value="Male"> Male<BR>
<INPUT type="radio" name="sex" value="Female"> Female<BR>
<BUTTON name="submit" value="submit" type="submit">
Send<IMG src="/icons/wow.gif" alt="wow"></BUTTON>
<BUTTON name="reset" type="reset">
Reset<IMG src="/icons/oops.gif" alt="oops"></BUTTON>
</P>
</FORM>
Recall that authors must provide alternate text for an IMG element.
It is illegal to associate an image map with an IMG that appears as the contents of a BUTTON element.
ILLEGAL EXAMPLE:
The following is not legal HTML.
<BUTTON> <IMG src="foo.gif" usemap="..."> </BUTTON>
17.6 The SELECT, OPTGROUP, and OPTION elements
<!ELEMENT SELECT - - (OPTGROUP|OPTION)+ -- option selector --> <!ATTLIST SELECT %attrs; -- %coreattrs, %i18n, %events -- name CDATA #IMPLIED -- field name -- size NUMBER #IMPLIED -- rows visible -- multiple (multiple) #IMPLIED -- default is single selection -- disabled (disabled) #IMPLIED -- unavailable in this context -- tabindex NUMBER #IMPLIED -- position in tabbing order -- onfocus %Script; #IMPLIED -- the element got the focus -- onblur %Script; #IMPLIED -- the element lost the focus -- onchange %Script; #IMPLIED -- the element value was changed -- >
Start tag: required, End tag: required
SELECT Attribute definitions
- name = cdata [CI]
- This attribute assigns the control name.
- size = number [CN]
- If a SELECT element is presented as a scrolled list box, this attribute specifies the number of rows in the list that should be visible at the same time. Visual user agents are not required to present a SELECT element as a list box; they may use any other mechanism, such as a drop-down menu.
- multiple [CI]
- If set, this boolean attribute allows multiple selections. If not set, the SELECT element only permits single selections.
The SELECT element creates a menu. Each choice offered by the menu is represented by an OPTION element. A SELECT element must contain at least one OPTION element.
The OPTGROUP element allows authors to group choices logically. This is particularly helpful when the user must choose from a long list of options; groups of related choices are easier to grasp and remember than a single long list of options. In HTML 4.0, all OPTGROUP elements must be specified directly within a SELECT element (i.e., groups may not be nested).
17.6.1 Preselected options
Zero or more choices may be pre-selected for the user. User agents should determine which choices are pre-selected as follows:
If no OPTION element has
the selected attribute set,
no options should be pre-selected.
| If one OPTION element has
the selected attribute set,
it should be pre-selected.
| If the SELECT element has
the multiple attribute
set and more than one OPTION element has
the selected attribute set,
they should all be pre-selected.
| It is considered an error if more than one OPTION element has the selected attribute set and the SELECT element does not have the multiple attribute set. User agents may vary in how
they handle this error, but should not pre-select more than one choice.
| |
<!ELEMENT OPTGROUP - - (OPTION)+ -- option group --> <!ATTLIST OPTGROUP %attrs; -- %coreattrs, %i18n, %events -- disabled (disabled) #IMPLIED -- unavailable in this context -- label %Text; #REQUIRED -- for use in hierarchical menus -- >
Start tag: required, End tag: required
OPTGROUP Attribute definitions
Attributes defined elsewhere
Note. Implementors are advised that future versions of HTML may extend the grouping mechanism to allow for nested groups (i.e., OPTGROUP elements may nest). This will allow authors to represent a richer hierarchy of choices.
<!ELEMENT OPTION - O (#PCDATA) -- selectable choice --> <!ATTLIST OPTION %attrs; -- %coreattrs, %i18n, %events -- selected (selected) #IMPLIED disabled (disabled) #IMPLIED -- unavailable in this context -- label %Text; #IMPLIED -- for use in hierarchical menus -- value CDATA #IMPLIED -- defaults to element content -- >
Start tag: required, End tag: optional
OPTION Attribute definitions
- selected [CI]
- When set, this boolean attribute specifies that this option is pre-selected.
- value = cdata [CS]
- This attribute specifies the initial value of the control. If this attribute is not set, the initial value is set to the contents of the OPTION element.
- label = text [CS]
- This attribute allows authors to specify a shorter label for an option than the content of the OPTION element. When specified, user agents should use the value of this attribute rather than the content of the OPTION element as the option label.
Attributes defined elsewhere
When rendering a menu choice, user agents should use the value of the label attribute of the OPTION element as the choice. If this attribute is not specified, user agents should use the contents of the OPTION element.
The label attribute of the OPTGROUP element specifies the label for a group of choices.
In this example, we create a menu that allows the user to select which of seven software components to install. The first and second components are pre-selected but may be deselected by the user. The remaining components are not pre-selected. The size attribute states that the menu should only have 4 rows even though the user may select from among 7 options. The other options should be made available through a scrolling mechanism.
The SELECT is followed by submit and reset buttons.
<FORM action="http://somesite.com/prog/component-select" method="post">
<P>
<SELECT multiple size="4" name="component-select">
<OPTION selected value="Component_1_a">Component_1</OPTION>
<OPTION selected value="Component_1_b">Component_2</OPTION>
<OPTION>Component_3</OPTION>
<OPTION>Component_4</OPTION>
<OPTION>Component_5</OPTION>
<OPTION>Component_6</OPTION>
<OPTION>Component_7</OPTION>
</SELECT>
<INPUT type="submit" value="Send"><INPUT type="reset">
</P>
</FORM>
Only selected options will be successful (using the control name "component-select"). Note that where the value attribute is set, it determines the control's initial value, otherwise it's the element's contents.
In this example we use the OPTGROUP element to group choices. The following markup:
<FORM action="http://somesite.com/prog/someprog" method="post">
<P>
<SELECT name="ComOS">
<OPTGROUP label="PortMaster 3">
<OPTION label="3.7.1" value="pm3_3.7.1">PortMaster 3 with ComOS 3.7.1
<OPTION label="3.7" value="pm3_3.7">PortMaster 3 with ComOS 3.7
<OPTION label="3.5" value="pm3_3.5">PortMaster 3 with ComOS 3.5
</OPTGROUP>
<OPTGROUP label="PortMaster 2">
<OPTION label="3.7" value="pm2_3.7">PortMaster 2 with ComOS 3.7
<OPTION label="3.5" value="pm2_3.5">PortMaster 2 with ComOS 3.5
</OPTGROUP>
<OPTGROUP label="IRX">
<OPTION label="3.7R" value="IRX_3.7R">IRX with ComOS 3.7R
<OPTION label="3.5R" value="IRX_3.5R">IRX with ComOS 3.5R
</OPTGROUP>
</SELECT>
</FORM>
represents the following grouping:
PortMaster 3
3.7.1
3.7
3.5
PortMaster 2
3.7
3.5
IRX
3.7R
3.5R
Visual user agents may allow users to select from option groups through a hierarchical menu or some other mechanism that reflects the structure of choices.
A graphical user agent might render this as:
This image shows a SELECT element rendered as cascading menus. The top label of the menu displays the currently selected value (PortMaster 3, 3.7.1). The user has unfurled two cascading menus, but has not yet selected the new value (PortMaster 2, 3.7). Note that each cascading menu displays the label of an OPTGROUP or OPTION element.
17.7 The TEXTAREA element
<!ELEMENT TEXTAREA - - (#PCDATA) -- multi-line text field --> <!ATTLIST TEXTAREA %attrs; -- %coreattrs, %i18n, %events -- name CDATA #IMPLIED rows NUMBER #REQUIRED cols NUMBER #REQUIRED disabled (disabled) #IMPLIED -- unavailable in this context -- readonly (readonly) #IMPLIED tabindex NUMBER #IMPLIED -- position in tabbing order -- accesskey %Character; #IMPLIED -- accessibility key character -- onfocus %Script; #IMPLIED -- the element got the focus -- onblur %Script; #IMPLIED -- the element lost the focus -- onselect %Script; #IMPLIED -- some text was selected -- onchange %Script; #IMPLIED -- the element value was changed -- >
Start tag: required, End tag: required
Attribute definitions
- name = cdata [CI]
- This attribute assigns the control name.
- rows = number [CN]
- This attribute specifies the number of visible text lines. Users should be able to enter more lines than this, so user agents should provide some means to scroll through the contents of the control when the contents extend beyond the visible area.
- cols = number [CN]
- This attribute specifies the visible width in average character widths. Users should be able to enter longer lines than this, so user agents should provide some means to scroll through the contents of the control when the contents extend beyond the visible area. User agents may wrap visible text lines to keep long lines visible without the need for scrolling.
Attributes defined elsewhere
The TEXTAREA element creates a multi-line text input control. User agents should use the contents of this element as the initial value of the control and should render this text initially.
This example creates a TEXTAREA control that is 20 rows by 80 columns and contains two lines of text initially. The TEXTAREA is followed by submit and reset buttons.
<FORM action="http://somesite.com/prog/text-read" method="post"> <P> <TEXTAREA name="thetext" rows="20" cols="80"> First line of initial text. Second line of initial text. </TEXTAREA> <INPUT type="submit" value="Send"><INPUT type="reset"> </P> </FORM>
Setting the readonly attribute allows authors to display unmodifiable text in a TEXTAREA. This differs from using standard marked-up text in a document because the value of TEXTAREA is submitted with the form.
17.8 The ISINDEX element
ISINDEX is deprecated. This element creates a single-line text input control. Authors should use the INPUT element to create text input controls.
See the Transitional DTD for the formal definition.
Attribute definitions
- prompt = text [CS]
- Deprecated. This attribute specifies a prompt string for the input field.
Attributes defined elsewhere
id, class
(document-wide
identifiers)
| lang
(language
information), dir
(text direction)
| title
(element title)
| style
(inline style
information)
| |
The ISINDEX element creates a single-line text input control that allows any number of characters. User agents may use the value of the prompt attribute as a title for the prompt.
DEPRECATED EXAMPLE:
The following ISINDEX declaration:
<ISINDEX prompt="Enter your search phrase: ">
could be rewritten with INPUT as follows:
<FORM action="..." method="post"> <P>Enter your search phrase: <INPUT type="text"></P> </FORM>
Semantics of ISINDEX. Currently, the semantics for ISINDEX are only well-defined when the base URI for the enclosing document is an HTTP URI. In practice, the input string is restricted to Latin-1 as there is no mechanism for the URI to specify a different character set.
17.9 Labels
Some form controls automatically have labels associated with them (press buttons) while most do not (text fields, checkboxes and radio buttons, and menus).
For those controls that have implicit labels, user agents should use the value of the value attribute as the label string.
The LABEL element is used to specify labels for controls that do not have implicit labels,
17.9.1 The LABEL element
<!ELEMENT LABEL - - (%inline;)* -(LABEL) -- form field label text --> <!ATTLIST LABEL %attrs; -- %coreattrs, %i18n, %events -- for IDREF #IMPLIED -- matches field ID value -- accesskey %Character; #IMPLIED -- accessibility key character -- onfocus %Script; #IMPLIED -- the element got the focus -- onblur %Script; #IMPLIED -- the element lost the focus -- >
Start tag: required, End tag: required
Attribute definitions
- for = idref [CS]
- This attribute explicitly associates the label being defined with another control. When present, the value of this attribute must be the same as the value of the id attribute of some other control in the same document. When absent, the label being defined is associated with the element's contents.
Attributes defined elsewhere
The LABEL element may be used to attach information to controls. Each LABEL element is associated with exactly one form control.
The for attribute associates a label with another control explicitly: the value of the for attribute must be the same as the value of the id attribute of the associated control element. More than one LABEL may be associated with the same control by creating multiple references via the for attribute.
This example creates a table that is used to align two text input controls and their associated labels. Each label is associated explicitly with one text input:
<FORM action="..." method="post">
<TABLE>
<TR>
<TD><LABEL for="fname">First Name</LABEL>
<TD><INPUT type="text" name="firstname" id="fname">
<TR>
<TD><LABEL for="lname">Last Name</LABEL>
<TD><INPUT type="text" name="lastname" id="lname">
</TABLE>
</FORM>
This example extends a previous example form to include LABEL elements.
<FORM action="http://somesite.com/prog/adduser" method="post">
<P>
<LABEL for="firstname">First name: </LABEL>
<INPUT type="text" id="firstname"><BR>
<LABEL for="lastname">Last name: </LABEL>
<INPUT type="text" id="lastname"><BR>
<LABEL for="email">email: </LABEL>
<INPUT type="text" id="email"><BR>
<INPUT type="radio" name="sex" value="Male"> Male<BR>
<INPUT type="radio" name="sex" value="Female"> Female<BR>
<INPUT type="submit" value="Send"> <INPUT type="reset">
</P>
</FORM>
To associate a label with another control implicitly, the control element must be within the contents of the LABEL element. In this case, the LABEL may only contain one control element. The label itself may be positioned before or after the associated control.
In this example, we implicitly associate two labels with two text input controls:
<FORM action="..." method="post"> <P> <LABEL> First Name <INPUT type="text" name="firstname"> </LABEL> <LABEL> <INPUT type="text" name="lastname"> Last Name </LABEL> </P> </FORM>
Note that this technique cannot be used when a table is being used for layout, with the label in one cell and its associated control in another cell.
When a LABEL element receives focus, it passes the focus on to its associated control. See the section below on access keys for examples.
Labels may be rendered by user agents in a number of ways (e.g., visually, read by speech synthesizers, etc.)
17.10 Adding structure to forms: the FIELDSET and LEGEND elements
<!-- #PCDATA is to solve the mixed content problem, per specification only whitespace is allowed there! --> <!ELEMENT FIELDSET - - (#PCDATA,LEGEND,(%flow;)*) -- form control group --> <!ATTLIST FIELDSET %attrs; -- %coreattrs, %i18n, %events -- > <!ELEMENT LEGEND - - (%inline;)* -- fieldset legend --> <!ENTITY % LAlign "(top|bottom|left|right)"> <!ATTLIST LEGEND %attrs; -- %coreattrs, %i18n, %events -- accesskey %Character; #IMPLIED -- accessibility key character -- >
Start tag: required, End tag: required
LEGEND Attribute definitions
- align = top|bottom|left|right [CI]
- Deprecated. This attribute specifies the position of the legend with
respect to the fieldset. Possible values:
top: The legend is at the top of the fieldset. This is the default value. bottom: The legend is at the bottom of the fieldset. left: The legend is at the left side of the fieldset. right: The legend is at the right side of the fieldset.
Attributes defined elsewhere
The FIELDSET element allows authors to group thematically related controls and labels. Grouping controls makes it easier for users to understand their purpose while simultaneously facilitating tabbing navigation for visual user agents and speech navigation for speech-oriented user agents. The proper use of this element makes documents more accessible.
The LEGEND element allows authors to assign a caption to a FIELDSET. The legend improves accessibility when the FIELDSET is rendered non-visually.
In this example, we create a form that one might fill out at the doctor's office. It is divided into three sections: personal information, medical history, and current medication. Each section contains controls for inputting the appropriate information.
<FORM action="..." method="post">
<P>
<FIELDSET>
<LEGEND>Personal Information</LEGEND>
Last Name: <INPUT name="personal_lastname" type="text" tabindex="1">
First Name: <INPUT name="personal_firstname" type="text" tabindex="2">
Address: <INPUT name="personal_address" type="text" tabindex="3">
...more personal information...
</FIELDSET>
<FIELDSET>
<LEGEND>Medical History</LEGEND>
<INPUT name="history_illness"
type="checkbox"
value="Smallpox" tabindex="20"> Smallpox
<INPUT name="history_illness"
type="checkbox"
value="Mumps" tabindex="21"> Mumps
<INPUT name="history_illness"
type="checkbox"
value="Dizziness" tabindex="22"> Dizziness
<INPUT name="history_illness"
type="checkbox"
value="Sneezing" tabindex="23"> Sneezing
...more medical history...
</FIELDSET>
<FIELDSET>
<LEGEND>Current Medication</LEGEND>
Are you currently taking any medication?
<INPUT name="medication_now"
type="radio"
value="Yes" tabindex="35">Yes
<INPUT name="medication_now"
type="radio"
value="No" tabindex="35">No
If you are currently taking medication, please indicate
it in the space below:
<TEXTAREA name="current_medication"
rows="20" cols="50"
tabindex="40">
</TEXTAREA>
</FIELDSET>
</FORM>
Note that in this example, we might improve the visual presentation of the form by aligning elements within each FIELDSET (with style sheets), adding color and font information (with style sheets), adding scripting (say, to only open the "current medication" text area if the user indicates he or she is currently on medication), etc. /samp
17.11 Giving focus to an element
In an HTML document, an element must receive focus from the user in order to become active and perform their tasks. For example, users must activate a link specified by the A element in order to follow the specified link. Similarly, users must give a TEXTAREA focus in order to enter text into it.
There are several ways to give focus to an element:
Designate the element with a pointing device.
| Navigate from one element to the next with the keyboard. The
document's author may define a tabbing order that specifies
the order in which elements will receive focus if the user navigates
the document with the keyboard (see tabbing
navigation). Once selected, an element may be activated by some
other key sequence.
| Select an element through an access
key (sometimes called "keyboard shortcut" or "keyboard
accelerator").
| |
17.11.1 Tabbing navigation
Attribute definitions
The tabbing order defines the order in which elements will receive focus when navigated by the user via the keyboard. The tabbing order may include elements nested within other elements.
Elements that may receive focus should be navigated by user agents according to the following rules:
- Those elements that support the tabindex attribute and assign a positive value to it are navigated first. Navigation proceeds from the element with the lowest tabindex value to the element with the highest value. Values need not be sequential nor must they begin with any particular value. Elements that have identical tabindex values should be navigated in the order they appear in the character stream.
- Those elements that do not support the tabindex attribute or support it and assign it a value of "0" are navigated next. These elements are navigated in the order they appear in the character stream.
- Elements that are disabled do not participate in the tabbing order.
The following elements support the tabindex attribute: A, AREA, BUTTON, INPUT, OBJECT, SELECT, and TEXTAREA.
In this example, the tabbing order will be the BUTTON, the INPUT elements in order (note that "field1" and the button share the same tabindex, but "field1" appears later in the character stream), and finally the link created by the A element.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"
"http://www.w3.org/TR/REC-html40/strict.dtd">
<HTML>
<HEAD>
<TITLE>A document with FORM</TITLE>
</HEAD>
<BODY>
...some text...
<P>Go to the
<A tabindex="10" href="http://www.w3.org/">W3C Web site.</A>
...some more...
<BUTTON type="button" name="get-database"
tabindex="1" onclick="get-database">
Get the current database.
</BUTTON>
...some more...
<FORM action="..." method="post">
<P>
<INPUT tabindex="1" type="text" name="field1">
<INPUT tabindex="2" type="text" name="field2">
<INPUT tabindex="3" type="submit" name="submit">
</P>
</FORM>
</BODY>
</HTML>
Tabbing keys. The actual key sequence that causes tabbing navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation and the "enter" key is used to activate a selected element).
User agents may also define key sequences to navigate the tabbing order in reverse. When the end (or beginning) of the tabbing order is reached, user agents may circle back to the beginning (or end).
17.11.2 Access keys
Attribute definitions
- accesskey = character [CN]
- This attribute assigns an access key to an element. An access key is a single character from the document character set.Note. Authors should consider the input method of the expected reader when specifying an accesskey.
Pressing an access key assigned to an element gives focus to the element. The action that occurs when an element receives focus depends on the element. For example, when a user activates a link defined by the A element, the user agent generally follows the link. When a user activates a radio button, the user agent changes the value of the radio button. When the user activates a text field, it allows input, etc.
The following elements support the accesskey attribute: A, AREA, BUTTON, INPUT, LABEL, and LEGEND, and TEXTAREA.
This example assigns the access key "U" to a label associated with an INPUT control. Typing the access key gives focus to the label which in turn gives it to the associated control. The user may then enter text into the INPUT area.
<FORM action="..." method="post"> <P> <LABEL for="fuser" accesskey="U"> User Name </LABEL> <INPUT type="text" name="user" id="fuser"> </P> </FORM>
In this example, we assign an access key to a link defined by the A element. Typing this access key takes the user to another document, in this case, a table of contents.
<P><A accesskey="C"
rel="contents"
href="http://someplace.com/specification/contents.html">
Table of Contents</A>
The invocation of access keys depends on the underlying system. For instance, on machines running MS Windows, one generally has to press the "alt" key in addition to the access key. On Apple systems, one generally has to press the "cmd" key in addition to the access key.
The rendering of access keys depends on the user agent. We recommend that authors include the access key in label text or wherever the access key is to apply. User agents should render the value of an access key in such a way as to emphasize its role and to distinguish it from other characters (e.g., by underlining it).
17.12 Disabled and read-only controls
In contexts where user input is either undesirable or irrelevant, it is important to be able to disable a control or render it read-only. For example, one may want to disable a form's submit button until the user has entered some required data. Similarly, an author may want to include a piece of read-only text that must be submitted as a value along with the form. The following sections describe disabled and read-only controls.
17.12.1 Disabled controls
Attribute definitions
When set, the disabled attribute has the following effects on an element:
Disabled controls do not receive focus.
| Disabled controls are skipped in tabbing navigation.
| Disabled controls cannot be successful.
| |
The following elements support the disabled attribute: BUTTON INPUT, OPTGROUP, OPTION, SELECT, and TEXTAREA.
This attribute is inherited but local declarations override the inherited value.
How disabled elements are rendered depends on the user agent. For example, some user agents "gray out" disabled menu items, button labels, etc.
In this example, the INPUT element is disabled. Therefore, it cannot receive user input nor will its value be submitted with the form.
<INPUT disabled name="fred" value="stone">
17.12.2 Read-only controls
Attribute definitions
The readonly attribute specifies whether the control may be modified by the user.
When set, the readonly attribute has the following effects on an element:
Read-only elements receive focus but cannot be modified by the user.
| Read-only elements are included in tabbing navigation.
| Read-only elements may be successful.
| |
The following elements support the readonly attribute: INPUT, TEXT, PASSWORD, and TEXTAREA.
How read-only elements are rendered depends on the user agent.
17.13 Form submission
The following sections explain how user agents submit form data to form processing agents.
17.13.1 Form submission method
The method attribute of the FORM element specifies the HTTP method used to send the form to the processing agent. This attribute may take two values:
get: With the HTTP "get" method, the form data set is appended
to the URI specified by the action
attribute and this new URI is sent to the processing agent.
| post: With the HTTP "post" method, the
form data set is included
in the body of the form and sent to the processing agent.
| |
The "get" method should be used when the form is idempotent (i.e., causes no side-effects). Many database searches have no visible side-effects and make ideal applications for the "get" method.
If the service associated with the processing of a form causes side effects (for example, if the form modifies a database or subscription to a service), the "post" method should be used.
Note. The "get" method restricts form data set values to ASCII characters. Only the "post" method (with enctype="multipart/form-data") is specified to cover the entire [ISO10646] character set.
17.13.2 Successful controls
A successful control is "valid" for submission. Every successful control has its control name paired with its current value as part of the submitted form data set. A successful control must be defined within a FORM element and must have a control name.
However:
Controls that are disabled cannot be
successful.
| If a form contains more than one submit
button, only the activated submit button is successful.
| All "on" checkboxes may be successful.
| For radio buttons that share
the same value of the name
attribute, only the "on" radio button may be successful.
| For menus, the control name is provided by a SELECT element and values are provided by OPTION elements. Only selected options
may be successful.
|
The current value of a file select is a list of one
or more file names. Upon
submission of the form, the contents of each file
are submitted with the rest of the form data. The file
contents are packaged according to the
form's content type.
| The current value of an object control is determined by
the object's implementation.
| |
If a control doesn't have a current value when the form is submitted, user agents are not required to treat it as a successful control.
Furthermore, user agents should not consider the following controls successful:
Reset buttons.
|
OBJECT elements whose declare attribute has been set.
| |
Hidden controls and controls that are not rendered because of style sheet settings may still be successful. For example:
<FORM action="..." method="post">
<P>
<INPUT type="password" style="display:none"
name="invisible-password"
value="mypassword">
</FORM>
will still cause a value to be paired with the name "invisible-password" and submitted with the form.
17.13.3 Processing form data
When the user submits a form (e.g., by activating a submit button), the user agent processes it as follows.
Step one: Identify the successful controls
Step two: Build a form data set
A form data set is a sequence of control-name/current-value pairs constructed from successful controls
Step three: Encode the form data set
The form data set is then encoded according to the content type specified by the enctype attribute of the FORM element.
Step four: Submit the encoded form data set
Finally, the encoded data is sent to the processing agent designated by the action attribute using the protocol specified by the method attribute.
This specification does not specify all valid submission methods or content types that may be used with forms. However, HTML 4.0 user agents must support the established conventions in the following cases:
If the method is "get"
and the action is an HTTP URI, the user agent
takes the value of action, appends a
`?' to it, then appends the form
data set, encoded using the
"application/x-www-form-urlencoded"
content type. The user agent then traverses the link to this
URI. In this scenario, form data are restricted to ASCII codes.
| If the method is "post" and
the action is an HTTP URI,
the user agent conducts an HTTP "post" transaction using the value of
the action attribute and a message
created according to the content
type specified by the enctype
attribute.
| |
For any other value of action or method, behavior is unspecified.
User agents should render the response from the HTTP "get" and "post" transactions.
17.13.4 Form content types
The enctype attribute of the FORM element specifies the content type used to encode the form data set for submission to the server. User agents must support the content types listed below. Behavior for other content types is unspecified.
Please also consult the section on escaping ampersands in URI attribute values.
application/x-www-form-urlencoded
This is the default content type. Forms submitted with this content type must be encoded as follows:
- Control names and values are escaped. Space characters are replaced by `+', and then reserved characters are escaped as described in [RFC1738], section 2.2: Non-alphanumeric characters are replaced by `%HH', a percent sign and two hexadecimal digits representing the ASCII code of the character. Line breaks are represented as "CR LF" pairs (i.e., `%0D%0A').
- The control names/values are listed in the order they appear in the document. The name is separated from the value by `=' and name/value pairs are separated from each other by `&'.
multipart/form-data
Note. Please consult [RFC1867] for additional information about file uploads, including backwards compatibility issues, the relationship between "multipart/form-data" and other content types, performance issues, etc.
Please consult the appendix for information about security issues for forms.
The content type "application/x-www-form-urlencoded" is inefficient for sending large quantities of binary data or text containing non-ASCII characters. The content type "multipart/form-data" should be used for submitting forms that contain files, non-ASCII data, and binary data.
The content "multipart/form-data" follows the rules of all multipart MIME data streams as outlined in [RFC2045]. The definition of "multipart/form-data" is available at the [IANA] registry.
A "multipart/form-data" message contains a series of parts, each representing a successful control. The parts are sent to the processing agent in the same order the corresponding controls appear in the document stream. Part boundaries should not occur in any of the data; how this is done lies outside the scope of this specification.
As with all multipart MIME types, each part has an optional "Content-Type" header that defaults to "text/plain". User agents should supply the "Content-Type" header, accompanied by a "charset" parameter.
Each part is expected to contain:
- a "Content-Disposition" header whose value is "form-data".
- a name attribute specifying the control name of the corresponding control. Control names originally encoded in non-ASCII character sets may be encoded using the method outlined in [RFC2045].
Thus, for example, for a control named "mycontrol", the corresponding part would be specified:
Content-Disposition: form-data; name="mycontrol"
As with all MIME transmissions, "CR LF" (i.e., `%0D%0A') is used to separate lines of data.
Each part may be encoded and the "Content-Transfer-Encoding" header supplied if the value of that part does not conform to the default (7BIT) encoding (see [RFC2045], section 6)
If the contents of a file are submitted with a form, the file input should be identified by the appropriate content type (e.g., "application/octet-stream"). If multiple files are to be returned as the result of a single form entry, they should be returned as "multipart/mixed" embedded within the "multipart/form-data".
The user agent should attempt to supply a file name for each submitted file. The file name may be specified with the "filename" parameter of the 'Content-Disposition: form-data' header, or, in the case of multiple files, in a 'Content-Disposition: file' header of the subpart. If the file name of the client's operating system is not in US-ASCII, the file name might be approximated or encoded using the method of [RFC2045]. This is convenient for those cases where, for example, the uploaded files might contain references to each other (e.g., a TeX file and its ".sty" auxiliary style description).
The following example illustrates "multipart/form-data" encoding. Suppose we have the following form:
<FORM action="http://server.dom/cgi/handle"
enctype="multipart/form-data"
method="post">
<P>
What is your name? <INPUT type="text" name="submit-name"><BR>
What files are you sending? <INPUT type="file" name="files"><BR>
<INPUT type="submit" value="Send"> <INPUT type="reset">
</FORM>
If the user enters "Larry" in the text input, and selects the text file "file1.txt", the user agent might send back the following data:
Content-Type: multipart/form-data; boundary=AaB03x --AaB03x Content-Disposition: form-data; name="submit-name" Larry --AaB03x Content-Disposition: form-data; name="files"; filename="file1.txt" Content-Type: text/plain ... contents of file1.txt ... --AaB03x--
If the user selected a second (image) file "file2.gif", the user agent might construct the parts as follows:
Content-Type: multipart/form-data; boundary=AaB03x --AaB03x Content-Disposition: form-data; name="submit-name" Larry --AaB03x Content-Disposition: form-data; name="files" Content-Type: multipart/mixed; boundary=BbC04y --BbC04y Content-Disposition: attachment; filename="file1.txt" Content-Type: text/plain ... contents of file1.txt ... --BbC04y Content-Disposition: attachment; filename="file2.gif" Content-Type: image/gif Content-Transfer-Encoding: binary ...contents of file2.gif... --BbC04y-- --AaB03x--
