I have to retract on my previous sweeping statement that Meta Keywords are obsolete and are therefore should not be given any sort of attention.
A Search Engine Land study showed that Yahoo! and Ask showed signs of support for the meta keyword tag, something many SEO folks have dismissed as a waste of time and effort.
I have also been advocating that meta keywords are practically useless, after years of being the cornerstone of spammers who think planting all sorts of keyword combinations is the key: misspellings, caps and non-caps, singulars and plurals and completely out of context phrases.
Danny Sullivan is a good resource of extensive study of different SEO issues, often expanding them to give a better understanding from the basics to the advanced features. While everyone can do what he did, he was the only one I knew who provided such comprehensive and highly credible coverage of the study.
In the study he made not too long ago, he inserted a fairly unique set of phrases on the SEL homepage:
On the Search Engine Land home page, I inserted this meta keywords tag:
The tag went up on August 28.
It took two days, until August 30, for Google to show the latest version of my page in its index. I searched for each of the words, and my home page didn’t come up. The meta keyword tag was not used for retrieval and thus not supported.
Microsoft Live: No
It took five days, until September 2, for Microsoft to show a version of my page with the meta keywords tag on it. As an aside, Microsoft is kind of annoying. It will say something like this in the cached copy of the page:
It took two days, until August 30, for Yahoo to have my latest page. Searches there did bring up the home page for all words. So the meta keywords tag IS used for retrieval.
Ask took the longest to show the most current version of my page, not reflecting the changes until today. Actually, when I look at the cached copy even now, it says that the page is from August 13 and uses a redirection URL rather than my http://searchengineland.com address.
Now, as we look at these findings, we realize that meta keywords are not as obsolete as what we think. But then again, its importance may not be significant enough to raise our enthusiasm about putting more efforts on it. The placement of keywords help, but don’t expect much promise from it. After all, when Danny did the study, he had to use a series of characters and not any recognizable keyword to make his effort work.