Google owes its swelling popularity to deft algorithms that quickly divine what’s useful on the Web. But there’s more to it than that. At Google, purity matters. Over the years, Brin and Page have resisted pressure to run banners, opting instead for haiku-like text ads and unintrusive sponsored links. They’ve taken a stand against pop-ups and pop-unders and refused ads from sites they consider to be overly negative. All the while, they’ve stubbornly kept the Google homepage concise and pristine.