One thing I really hate in SEO is the minor things that get made into big majors. Page Rank is one thing that springs to mind, the less said about that the better. The ultimate criminal has to be the Keywords Meta Tag. In fact it is so pointless it won't make a blind bit of difference to Google whether it's there or not. Annoyingly it's something which just seems to have 'hung around' from the dark days of spammy SEO.
What's the Keywords Meta Tag for?
Back in the early 90's when Search Engines emerged on the scene to catalog and put some order on the growing number of web pages popping up, meta tags were used as useful way for a web site to tell the engine what it was about. Due to the popularity of Search Engines this system was readily abused and most web sites started having meta tags about popular subjects they had nothing to do with like "Britney Spears".
That's the simple history of the Keywords Meta Tag. In the mid 90's some of the Search Technology which we see today started and one of the key changes was that the Search Engine Spider popped up, this is an automated program (bot) that would index pages.
In some cases your Keyword Meta Tag can actually damage your rankings so if you insist on using it here is a few pointers:
Don't Spam - make sure all keywords are mentioned at least once in your main content.
Don't use overkill - limit the number of keywords you use to no more than a dozen. ie don't have an endless list, the less really the better.
Don't be repetative - say if your site is about Dog Food don't have Dog Food this, Dog Food that, Dog Food more, Dog Food even more.
Instead each keyword should be unique - Dog Food, this, that, more, even.
If, in the case of the above example, Dog is not always connected to Food have a comma between.
Don't use overly specific keywords, if your targeting particular phrases you should include some general markets too
Make each page unique - variety is the spice of life, Google certainly think so.
Meta Description Tag
We should mention the meta description tag at this point, this is far more important (more on that in another post), so make sure your major keywords are mentioned here.