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 attribute 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
The "Generator" value for the NAME attribute is very commonly inserted
into documents by HTML editor programs. It specifies as a value the
name of the editor that generated the code. Web browsers ignore this
META element usage.
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.
HTTP allows the MIME type and character set/encoding to be specified as an
HTTP-header. Using a "Content-Type" value for the HTTP-EQUIV attribute
allows the same capability in HTML. Of greatest interest to authors will
be the ability to define the document's character set. HTTP 1.1 requires the
"charset" value to be honored, but also states that some older HTTP 1.0
clients will not understand it. See
Assigned Numbers" - Sec: Character Sets and RFC 2045: Multipurpose
Internet Mail Extensions - Sec: 2.2 for more information.
The "Pragma" value for the HTTP-EQUIV attribute specifies caching
behavior. Several values are possible for this HTTP-header, but the
value of most use to authors will be "no-cache." When this is used
as the value for the CONTENT attribute, the document may not be
cached (well, SHOULD not be...) by a caching system anywhere
along the connection chain between the browser and the source
document. A browser emits the same Pragma HTTP header to a
document's source location when a user requests the document to be
reloaded. HTTP 1.1 replaces "Pragma: no-cache" with
"Cache-Control: no-cache", but understands "Pragma" as well. For more
information on caching, take a look at
The "Expires" value for the HTTP-EQUIV attribute gives as its CONTENT
value a date [Date Value]. The Expiration 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. Setting the
CONTENT attribute to a date in the past, or even to an illegal value
of "0" tells the browser to always look for a new version of the page.
For more information on caching, take a look at
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.
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' CSS property syntax that IE also supports.
content="Duration=[Duration],Transition=[Transition Type]" />
[Event] is one of:
Site-Enter, or Site-Exit
[Duration] is a floating point value
specifying the transition time in seconds.milliseconds
[Transition Type] is an
integer from 0 to 23 representing a transition effect (consult links below.)