Today in Google’s Webmaster Central Blog, Matt Cutts explains:

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.

There has been a long debate over the years whether Google would use the meta keywords section of web pages in their ranking algorithm. This blog post by Google has now ended this discussion (except for the conspiracy theorists). Matt goes on to explain that Google has ignored this tag for years, as people were often abusing this list of keywords by stuffing in non-related words.

What About the Meta Description Tag?

Google does use this tag, but not for ranking purposes:

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.

So it still makes sense to have the Meta Description be a one or two sentence summary of each web page.

What About Bing?

Bing is a little more “mysterious” about whether they use this tag in their ranking algorithm:

The <meta> tag’s keyword attribute is not the page rank panacea it once was back in the prehistoric days of Internet search. It was abused far too much and lost most of its cachet. But there’s no need to ignore the tag. Take advantage of all legitimate opportunities to score keyword credit, even when the payoff is relatively low.

So, they seem to indicate it has minimal impact, but they stop short of saying it is completely ignored.

Use Meta Keywords or Not Then?

Our opinion – It cannot hurt to put a few keywords in this meta tag that accurately reflect the content on your pages. However, do not agonize over or spend too much time on this tag. Instead, focus on more important SEO considerations such as Title tags, H1 tags, Keyword Density throughout the page, and obtaining quality inbound links to your pages.

And of course…. Great and often updated content.