I have realized that in general, Google tries to provide a good mixture of links on the first page from the following: 1. Authority websites 2. Forums 3. Videos 4. Blogs 5. News 6. Images 7. More that I can't think of right now Now it is not always that all these types of site links will be there on the first page. What I believe is that suppose, for instance, a forum has somewhat less "SEO rating" in the eyes of Google (based on parameters like backlinks, PR etc.) and with the normal SEO rating, there aren't any forums on the first page of google, then Google lowers the threshold and includes the forum in the top 10 result. Similar will be the case with other types of sites. What do you think?