Google's official advice for boosting a website's presence in Google search results has been the same for years: "Have other relevant sites link to yours.” The search engine's original PageRank formula was based entirely on which pages link to which other pages — a mathematical analogy to real-world reputations. But Google has removed its original rule from the latest revision of its Webmaster Guidelines. Why?Brian Ussery, who noted the change on his blog, is a professional search-engine optimization (SEO) consultant — he helps website owners raise their Google rank. Ussery thinks Google has "a renewed emphasis on rooting out paid links passing PageRank and/or low quality links." Years ago, site marketers realized that they could simply pay "relevant" sites — say, the site that comes up first for "Pacific Heights real estate" — to link to their own sites, boosting their own rank in Google results. When Google employees said, "Have other relevant sites link to yours," they meant "build a site that people who run other relevant sites will consider worth linking to." What they didn't mean was "pay them to link to your crummy site." As Ussery implies, that's pretty much how everyone does business on the Internet now. Google's graph of all the Web's links, once an elegant directory of reputation, has been corrupted by payola. What does Google want? Their guidelines should spell it out: Dear Webmasters, please stop spending your budget buying links. Instead, buy our ads.