Google made historic news yesterday by declaring they do not use the meta keywords tag. They haven't used the meta keywords tag for an incredibly long time and any "SEO" should know that.

I guess they want to focus on high-quality-posts ,and preventing low-quality post or copied posts trying to cheat ranking-system by any SEO method .

So there are official posts from Matt Cutts, the Google Blog and Search Engine Land .We can trust this information is true ,not a joke .

If you want to know which meta tags Google does pay attention to, see this FAQ. Plus, Googler's JohnMu tweeted that Google also does "not adhere to the "revisit-after" meta tag," if you wanted to know.

Finally, here is a video on Google Blog