BTW About 12 years ago I was building this search engine, and I was toying with the idea of building a classifier that classifies web pages based on their "genre" rather than category, so you can limit your search for shopping websites, forums, blogs, news sites, social media, etc. It was a bitch to train, and my classifier's algorithm was pretty crappy, but it showed some potential.

I think today modern search engine do that behind the scene, and try to diversify the result to include pages from multiple genres, but they usually don't let you choose.