Google announced – they don’t use the keywords tag in their search engine. Here is a video explaining why:
Keywords tag is meaningful only in the world of search engine optimization. It tells the search engines – "hey, this site is related to these words". Some webmasters use tons of incoherent and misleading keywords to get more traffic so most SE drop it some years ago.
Matt Cutts: Google doesn’t use the keywords meta tag in web search
Google Webmaster Central Blog: Google does not use the keywords meta tag in web ranking