Web Design in a Nutshell, 3rd Edition

http-equiv

Information provided by an http-equiv attribute is processed as though it had come from an HTTP response header. HTTP headers contain information the server passes to the browser just before it sends the HTML document, such as media type information and other values that affect the action of the browser. Therefore, the http-equiv attribute provides information that will, depending on the description, affect the way the browser handles your document.

Tip

An HTTP header is not the same as the header indicated by the head element within the HTML document. HTTP headers exist outside the HTML text document and are tacked on by the server. When a document is requested via an HTTP request (that is, via the Web), the HTTP header goes along for the ride to give the browser a heads-up on what kind of document to expect. Its contents are not displayed.

There is a large number of predefined http-equiv types available. This chapter introduces just a few of the most useful. For a complete listing, see the Dictionary of HTML META Tags at http://vancouver-webpages.com/META.