Matt Cutts, Google software engineer:
Google is not using meta-keywords tag at all because keywords are mostly used to spam search engines.
Google is not using the meta-description tag for ranking. Sometimes the meta-description tag is used for the site-snippet in search results if part of the content does not fit. But mostly meta-description is generated automatically from the content of the page and meta-description is the same as beginning of the content of the page.
Google has dropped the support of meta-keywords and meta-description tags for search ranking. The main reason why Google has dropped the support of keyword and description meta tags is because user will never see them on page so it is not logical to use them for page ranking. Google handles about 92% of all search queries in the world. So now web-developers may stop using meta-keywords and meta-description meta tags, because spending time on them is not worth it.
- Google Webmasters Blog about meta tags support by Google
- Video with Matt Cutts about meta tags support by Google
- StatCounter Search Engines stats usage - Google handles about 92% of all search queries in the world
- General notes on Search Engines Optimization