Simple question: what is keyword stuffing? What is the recommended number of unique keywords to use in your meta tag per page? In forums ppl say 2-3 per page. In books I've seen 8-10 per page. I just want to know in numerical terms what is considered keyword stuffing. Thanks.
The answer will depend on the context and variety of the keyword(s). Any search engine worth its salt will tolerate and reward more keywords if it determines that they appear where they should in a grammatically and semantically sound sentence. For example, if you are just listing words, 2-3 is your maximum. If you are actually delivering unique and valuable content, a higher number wouldn't set off any alarms.
That said, I hesitate to contribute to junk text designed solely to increase SEO. Quality content should be paramount.
Keywords stuffing is when you write text that is filled with lots of keywords but basically no content in order to attempt to fool search engines into thinking that your website is about some subject. This is a really bad idea, though, because in writing a blob of keyword text, you have made your website less useful to humans, and how relevant your website is to humans is what any good search engine will rate you on. So, in short, make your website relevant and useful, and SEO will automatically follow.