seo_4_u - 12:31 pm on Feb 16, 2007 (gmt 0)

There is no such rule to follow. But yes based on how competitive the keywords is that you want to target, the number of pages would vary.

Yet again, if you have optimized content for the keywords, then even a single page is enough to take on the world.

So, its up to you to select which option, more pages or more optimized content per page!