By most SEO professional's estimation, the keyword Meta HTML tag is dead. There is a general consensus around the Google SEO community that the days to manually improve your SEO results through Meta keyword stuffing are over. One used to be able to stuff the meta keywords tag with up to about 270 characters worth of keywords, which then helped improve the page's SEO results, it became so easy to do, that its overuse caused most search engines to decrease their importance in ranking or completely eliminate their ranking value altogether.
Now most search engines have a mathematical formula called an algorithm that takes several elements into account, assigns them a numerical value, compares them to other sites that are optimized or focused on the same or similar keywords and then gives it a ranking. The algorithm for each search engine is different but everyone in SEO agrees that Google's is the most complex and hardest to optimize for.
Because of the increased complexity of the Google algorithm, and the fact that it is always evolving and changing, oh yeah, and very secret, it has become a niche area few have mastered.
Since the Meta keyword is no longer useful in helping your site's ranking, focus on the elements that are:
1) Domain name which contains keywords you optimize for is helpful
2) A page title that contains the keyword you optimize for is important
3) The Meta description is where your creativity can shine. This is normally the punch line that draws people to your site from an Organic Search Result, and it is a great place to put your keywords so long as it makes sense.
4) Keep your content focused on the above three elements, but make it so it doesn't disrupt the flow of the information presented. (This when done incorrectly will cause ranking to drop).
As you can see, there are so many other elements than the Meta keywords tag, so all is not lost. Be careful when programing, be clear in the focus of your page and most important, and don't try methods that may otherwise hurt your Google SEO efforts.