In a post on the Google Webmaster Central blog today (Google does not use the keywords meta tag in web ranking), Google has clarified its policy on meta tags and page rank. Those of us trying to protect our clients from SEO/SEM snake-oil salesmen are happy to finally have an official statement from Google. In short, here it is:
There are many other variants of the meta tag, including some unique to Google. See the Google Webmaster help page discussing meta tags for a list of values Google supports (pay attention to the robots meta tag). Watch the video below for an explanation from a Google representative and his Threadless t-shirt.