<meta http-equiv="value" content="foo" />
META HTTP-EQUIV tags are the equivalent of HTTP headers.
When you open a new web page, a web server receives your browser’s request via HTTP (Hyper Text Transfer Protocol). The web server finds your page (or not) and then generates an HTTP response. The initial data in that response is called the “HTTP header block.” The header sends the browser information regarding the formatting and display of the page requested. There are other tags with meta information that are not technically meta tags, such as Title Tags and DTD (Document Type Declaration).
Just like normal headers, META HTTP-EQUIV tags usually guide the response of web browsers, and are used to further refine the information which is provided by the actual headers. In some browsers, even though the DTD declaration declares the character set, the page may not display properly if the meta-tag for character set also does not appear! HTTP-EQUIV tags affect the browser in exactly like normal headers. Certain servers may translate META HTTP-EQUIV tags into actual HTTP headers automatically so that the user’s Web browser would simply see them as normal headers. The Apache and CERN httpd servers, use a separate text file which contains meta-data. A few Web server-generated headers, such as “Date,” may not be overwritten by META tags.
<meta name="value" content="foo" />
META tags with a NAME attribute are used for META types which do not correspond to normal HTTP headers. There is still a lot of disagreement among developers, experts and just about everyone regarding how the various bots interpret tags which contain various attributes (especially keywords); whether they are declared as “name” or “http-equiv,”.
Are Meta Tags Obsolete?
Meta tags were designed for a simpler time and therefore many of the attributes and reasons thought up by the people who run the W3C turned out to be obsolete thanks to the later actions of search engine.
Some argue that meta keyword tags and even meta description tags are useless as the main innovation of Google was that it basically ignored meta tags, which were being extensively abused – and instead actually parsed the page to determine on-page content relevance, content and even keywords.