3.4 META

META is a general element for document meta-information -- that is, for information about the document that cannot be expressed by LINK, BASE or the other HEAD elements. There are two ways this can be expressed.

3.4.1 HTTP-Equivalent META Information

Sometimes you want a header to contain information that would ordinarily be returned by the server as a field in the HTTP headers. For example, you could use META to include an expiry date for files that are periodically updated. The META element would be:

   <META HTTP-EQUIV="Expires"   CONTENT="25-Dec-1995  12:00:00 GMT">

NOTE -- You should not use this element to override a header that is correctly sent by a server, as this will confuse the browser, or may confuse a proxy server lying between someone's browser and the site from which the document originates

Netscape (and Other) Extension to META

Netscape browsers support META elements of the form:

   <META HTTP-EQUIV="Refresh" CONTENT="12; URL=http://foo.bar/blatz.html">

Several browsers, including Netscape Navigator, Microsoft Internet Explorer and AOL 1.2.3 support this 'Refresh" header. With the above example, the browser will, after a delay of 12 seconds, access the indicated URL.

An alternative form is:

   <META HTTP-EQUIV="Refresh" CONTENT="10">

in which case the browser would wait 10 seconds and then re-access the currently displayed document.

3.4.2 Arbitrary User-Specified META Information

A user might want to include information about the document, such as keywords for indexing, the name of the author, and so on. This can be done with META elements such as the following:

   <META NAME="author"   CONTENT="Ian Graham">
   <META NAME="keywords" CONTENT="html documentation web url">
   <META NAME="editor"   CONTENT="HTML SuperPro">

The attribute NAME refers to arbitrary user-selected names, while HTTP-EQUIV means that the value has a real equivalent header in the HTTP protocol. Again this is only really useful given tools for processing these data. At present, there are very few tools that take advantage of META element content.

3.4.3 Commonly-Understood META Elements Formats

There are several other common META elements that are used to provide information to Web-indexing robots -- that is, the automated tools that retrieve Web pages and create searchable indexes, such as those found at Lycos, AltaVista, or Yahoo. Additional information about these special uses for META are found at http://vancouver-webpages.com/META/.