Re-post from the 
Webmaster Central Blog
Recently we received some questions about how Google uses (or more accurately, doesn’t use) the “keywords” meta tag in ranking web search results. Suppose you have two website owners, Alice and Bob. Alice runs a company called AliceCo and Bob runs BobCo. One day while looking at Bob’s site, Alice notices that Bob has copied some of the words that she uses in her “keywords” meta tag. Even more interesting, Bob has added the words “AliceCo” to his “keywords” meta tag. Should Alice be concerned?
At least for Google’s web search results currently (September 2009), the answer is no. Google doesn’t use the “keywords” meta tag in our web search ranking. This video explains more, or see the questions below.
Q: Does Google ever use the “keywords” meta tag in its web search ranking?
A: In a word, no. Google does sell a Google Search Appliance, and that product has the ability to match meta tags, which could include the keywords meta tag. But that’s an enterprise search appliance that is completely separate from our main web search. Our web search (the well-known search at Google.com that hundreds of millions of people use each day) disregards keyword metatags completely. They simply don’t have any effect in our search ranking at present.
Q: Why doesn’t Google use the keywords meta tag?
A: About a decade ago, search engines judged pages only on the content of web pages, not any so-called “off-page” factors such as the links pointing to a web page. In those days, keyword meta tags quickly became an area where someone could stuff often-irrelevant keywords without typical visitors ever seeing those keywords. Because the keywords meta tag was so often abused, many years ago Google began disregarding the keywords meta tag.
Q: Does this mean that Google ignores all meta tags?
A: No, Google does support several other meta tags. This meta tags page documents more info on several meta tags that we do use. For example, we do sometimes use the “description” meta tag as the text for our search results snippets, as this screenshot shows:
Even though we sometimes use the description meta tag for the snippets we show, we still don’t use the description meta tag in our ranking.
Q: Does this mean that Google will always ignore the keywords meta tag?
A: It’s possible that Google could use this information in the future, but it’s unlikely. Google has ignored the keywords meta tag for years and currently, we see no need to change that policy.