Google uses a global focus group of search-quality raters to assess the results returned by its search algorithms and ensure that search engine optimization spam isn't slipping through. An anonymous rater offers the inside scoop on the methods Google uses to police its rankings. "When looking at a site, I always check for spam signals first -- keyword stuffing, hidden text, sneaky redirects, and the like. ... I really just look at content and figure out if it would be a worthwhile page for a user to see," the rater explains.