I think it was a combination of: * A better search algorithm than the competition * Lack of paid-for search rankings, which were common-place previous to Goog

I think it was a combination of: * A better search algorithm than the competition * Lack of paid-for search rankings, which were common-place previous to Google * Tasteful, lightweight, fast design with a lack of intrusive banner ads All 3 are largely taken for granted these days.