Google Dance
Once in a month Google calculates the page rank of each page and changes the serp(search enigne result pages) for all keywords.....

Google PR Secrets Revealed
PageRank is Google’s measure of importance assigned to a web page on a scale of 1 to 10.

Yahoo! search tips for Webmasters
Yahoo has helpfully provided some tips on saving bandwidth for your sites, Yahoo slurp is known to hit hard on dynamic sites consuming a lot of bandwidth....