The Meta element is an extensible mechanism for use in identifying
specialized document meta-information. Each Meta element occurrence specifies a
Name/Value pair. If multiple Meta elements are specified with the same
name, their combined CONTENT sections should be concatenated as a comma
separated list to be associated with the common NAME value.
Current common uses
Client Pull:
This use of the META element causes a document to be automatically loaded
after a specified number of seconds. This form uses the HTTP-EQUIV
attribute as the identifier in the META statement with a value of REFRESH.
The content can be either an integer value [N] representing the number of
seconds to wait before refreshing the current page, or a combination value
separated by a semi-colon representing a time value [N] and a URL page
destination [URL].
Syntax 1: <metaHTTP-EQUIV="refresh"
CONTENT="[N]">
Syntax 2: <metaHTTP-EQUIV="refresh"
CONTENT="[N];
URL=[URL]">
Editor Identification:
The GENERATOR value for NAME is very commonly inserted into documents
by HTML editor programs. It specifies as a value the editor that
generated the code. Web browsers ignore this META element usage.
Syntax: <metaNAME="GENERATOR"
CONTENT="[Editor
Name]">
Search Engine Identification:
There are two commonly used META element syntaxes for helping in the
indexing of web documents in popular search engines. The KEYWORDS
value for the NAME attribute is a comma separated list of keywords
relating to the current document, while the DESCRIPTION value for
the NAME attribute represents the current document description
summary. Web browsers ignore this META element usage but some search
engine robots use it to help index files.
Syntax 1: <metaNAME="Keywords"
CONTENT="[Search
Engine Keywords]">
Syntax 2: <metaNAME="Description"
CONTENT="[Search
Engine Description]">
Browser Cache Override:
The EXPIRES value for the NAME attribute gives as its CONTENT value
a date [Date Value]. The EXPIRES value is used to indicate to a browser when
time-sensitive information becomes old. Browsers must not cache the
requested page beyond the date given. The presence of an EXPIRES
field does not imply that the original resource will change or cease
to exist at, before, or after the time indicated, but does speak to
the expected timeliness of the material.
Syntax 1: <metaHTTP-EQUIV="Expires"
CONTENT="[Date
Value]">
PICS Identification
The Platform for Internet Content
Selection [PICS] is a system designed to associate categorizing
labels with document content. The system originated as a method to
help control access to questionable content, but can also be used
to label and classify other types of document content as well, such
as code signing, privacy, and intellectual property rights management.
Syntax: Can vary quite a bit. Usually created
by going to a site and filling out a form. See
http://www.w3.org/PICS/Overview.html
for more details.
Inter-page Transition Filter Effects
This is a special syntax only allowed by Internet Explorer 4.0 and above to
allow special effects to occur while the page is loading or unloading. This
syntax uses the same filter syntax that IE4 supports via CSS (more information
on this syntax will be forthcoming, but see
Microsoft's
page on filters for more details.
Syntax: <metaHTTP-EQUIV="[event]"
CONTENT="Duration=[Seconds],Transition=[Transition Type]">
where [event] is one of: Page-Enter,
Page-Exit, Site-Enter, or
Site-Enter
and [event] is the transition time in seconds
and [Transition Type] is an integer from 0 to 23 representing
a transition effect (see Microsoft's site for more details on the various
transition effects.)
Specifies the value of the Name/Value pair. The values allowed for
this attribute are dependent on the NAME or HTTP-EQUIV attribute used.
Values: Alphanumeric string value.
HTTP-Equiv
2 | 3
| 3.2 | 4
| IE2 | M3
| N1.1 | O3
Required? No
Description:
This attribute binds the Meta CONTENT element to an HTTP header
field. When a browser requests a particular page containing a META
HTTP-Equiv element from a server, the CONTENT portion of the element
will be attached to the document header that is passed to the browser
before the rest of the actual document content. The browser or HTTP
server may use this information to process the document. Values are
not case sensitive.
Values: Alphanumeric keyword string value.
Name
2 | 3
| 3.2 | 4
| IE2 | M3
| N1.1 | O3
Required? No
Description:
An attribute that specifies the name of the Name/Value pair. If not
present, HTTP-EQUIV must be supplied in its place.
Values: Alphanumeric keyword string value.
Scheme
2 | 3
| 3.2 | 4
| IE | M
| N | O
Required? No
Description:
Indicates a pre-determined scheme/format to be used to interpret the
CONTENT attribute value in cases where multiple formats are supported.
Values: Dependent on the property name and the profile being used.
Url
2 | 3
| 3.2 | 4
| IE4 | M
| N | O
Required? No
Description:
Indicates the URL to reload after the time specified in the CONTENT attribute.
To help search engines better index your pages, the KEYWORDS and
DESCRIPTION values are strongly recommended to authors, especially for
use in top-level structure pages.