t2dman - 6:23 am on Jan 23, 2004 (gmt 0)

With knowledge of how Google ranks sites, you get an idea of how close serp 2, 3, etc are to you.

Keyword density is low on the list; text links in, page rank, position of keywords in title, and search phrase keyword proximity in the text are all much higher. The middle third of my page is dynamic according to the time of the day/week, yet my position for many competive phrases, including worldwide single word searches city/suburb/category is very constant, and improving due to the text links, pr etc. As long as you are very strong in all those other areas, and have a basic first paragraph of your site that never changes containing your keywords, my experience is that serps can be stable despite other wording changes.