Meta Keywords have been a strong point of contention for many years. Every web page has the option to include a "meta keywords" tag in the background code of the page. Many years ago these keywords were among the first ways search engines would rank a web page.
In the mid to late 1990's, website owners realized they could stuff multiple keywords into that meta tag to boost their search engine raking. Luckily the search engines figured this out and very quickly disavowed the meta keywords HTML tag.
Search engine optimization specialists have stated pros and cons against the continued practice of meta keywords.
Google never used the meta keyword tag for optimization.
In 2009, Yahoo announced that they didn't use meta keywords for ranking. It was thought that Bing didn't use them either.
In the summer of 2011, Bing announced that they were reading the meta tags again, but instead of reading them to help increase your page's search ranking, Bing is using the meta keyword to find spammers.
It almost seems like an upside down approach for a search engine, but Bing's point of view is that they look at your keywords for best practices. If you are overtly stuffing pointless keywords, then Bing will look a little closer to see what else you might be doing.
Keyword best practices are described as 5 to 7 keywords, but nothing repetitive or seemingly endless. That means no bonus plural versions, intentional misspellings, or using the same word in multiple phrases.
Last week we looked at H.Samuel, The Jeweler as a good example for correct meta description usage.
Let's look at their keywords:
"jewellery, diamond jewellery, wedding jewellery, engagement jewellery, branded watches, collectibles, gift ideas, forever diamonds, online jeweller, high street jeweller, h samuel jewellery, h samuel, hsamuel, h.samuel, hsamuels, h.samuels, samuals, h samuels jewellers, hm samuel, h. samuel, high street jeweller, online jeweller, h samuels, samuels jewellers, h samual, h samuel jewellers"
Eek! That's obviously keyword stuffed. Google would ignore this meta keywords stuffing as if it wasn't there. But apparently Bing will see the multiple variations of the word jewellery/jeweler and look deeper into other SEO infractions.
So there you have it. Meta Keywords are still useless, but if you feel inclined to use them, keep yourself limited to 7 words. Google won't notice, so they won't penalize you, but Bing may be particularly vindictive.