The Title tag is perhaps the most important meta tag for SEO. The description meta tag is also important. As at today, the keyword meta tag is not important as far as the major search engines like Google, Bing, and Yahoo are involved. However there is no harm in adding them. Meta Tags define particular things about a web page, for example, what character set to use when displaying the characters on the page, or what language the html document is written it, or how many long should be waited before refreshing the page or redirecting to another webpage. Major search engine's use Meta tags as major criteria for listing sites.