Yahoo has long been the only major search engine that supported the meta keywords tag. However, the search engine revealed on October 6th, 2009 that like the other majors, it no longer supports it.

The news came during the Ask The Search Engines session at SMX East in New York today. The search engines were all asked about their support of the tag. Moderator Danny Sullivan noted that only Yahoo provided support of the tag — prompting Cris Pierry, senior director of search at Yahoo, to announce that support actually had been ended unannounced “several” months ago.

<** update 11/15/09 **>
Danny Sullivan went and tested this after SMX and here is a excerpt from his findings:

“The test was simple. I placed a unique word in the meta keywords tag on the home page of Search Engine Land. This word — xcvteuflsowkldlslkslklsk — generated no results on Yahoo when I looked earlier this week. Today, when I searched, it brought back the Search Engine Land home page. Thus, Yahoo indeed indexes the content of that tag. (And to be clear, I looked before writing this article. In short order, this article itself, along with others, will appear because they’ll make use of that word).”

Bing doesn’t support the tag. Google has never supported it and in fact clarified this again in a special post last month. See Google: Stop Suing Over The Meta Keywords Tag, We Don’t Use It for more about that.