Via the Google Webmaster Tools blog (with accompanying YouTube video), Google’s Matt Cutts confirmed what many in the SEO community have known for quite some time: Google doesn’t use the meta keywords tag in their rankings.
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.
While left as almost an afterthought (and probably should have been highlighted a bit more), Cutts also confirms that the meta description tag also does not influence the Google search results.
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.
Google does not use the keywords meta tag in web ranking (Official Google Webmaster Tools Blog)
Google: Stop Suing Over The Keywords Tag, We Don’t Use It (Search Engine Land)