Meta Tags
Meta elements
Meta elements are the HTML or XHTML <meta … > element used to provide structured metadata about a Web page. Multiple elements are often used on the same page: the element is the same, but its attributes are different. Meta elements can be used to specify page description, keywords and any other metadata not provided through the other headelements and attributes.
The meta element has two uses: either to emulate the use of the HTTP response header, or to embed additional metadata within the HTML document.
With HTML up to and including HTML 4.01 and XHTML, there were four valid attributes: content, http-equiv, name and scheme. Under HTML 5 there are now five valid attributes: charset having been added. http-equiv is used to emulate the HTTP header. name to embed metadata. The value of the statement, in either case, is contained in the content attribute, which is the only required attribute unless charset is given. charset is used to indicate the character set of the document, and is available in HTML5.
Meta Title Tag
If you were teaching a novice about SEO, one of the first items on your agenda would be to give each of your pages a unique title, which is done in the Meta title tag. Re-titling pages is critical for several reasons, including being a key SEO optimization element. In addition, the title is what appears at the top of your browser and is often (though not always) what is displayed as the link in a search engine ranking. This makes the title tag an important element to optimize in order to improve usability on the website. Another often overlooked benefit of the page title is that it is an important web accessibility consideration.
Meta Description
The Meta description tag is what you most likely will see as your page description on the search engine results pages if the keyword that you are targeting appears in the Meta description tag. This offers a tremendous opportunity to help build on the theme for the page but also as a small bit of ad copy should your page rank for the keyword. A well written Meta description tag can increase your click through rates if your page is ranked for a keyword. Where the title tag grabs the attention of the user and tells him that your page has information he is looking for, the Meta description provides a "call to action" to click your link.
Meta Keywords
The Meta keywords tag was the first element that webmasters used to "spam" search engines. This technique did not work for long as the search engines quickly adapted and eventually most of them ceased to use this element as any part of their ranking algorithms. Since this is not true of all search engines and properly implemented Meta tags will not hurt your rankings, it is advisable to continue with proper Meta tag optimization.