CFCs, HCFCs, and Halon: The ozone layer is destroyed by CFC's, chlorofluorocarbons, that are used as a propellant in aerosol cans, and refrigerants in older cars and refrigerators. When Chlorofluorocarbons (Freon and other CFCs) and Bromofluorocarbons (Halons) they became popular refrigerants and fire fighting agents.
Anyways, let's come to out topic. Yahoo! Browser. Yahoo is the No.1 site on the web. Having the maximum traffic, it's still ruling in the laexa rank. Now, just to get all it's pages open properly and work nicely, Yahoo! joined hands with Microsoft in making a Yahoo! friendly browser. And here it is, YAHOO! Browser.
Answer Wiki. Yahoo was first with significant/useful semantic search feature (SearchMonkey), then Google and Bing added the similar functionality. Facebook is recently doing a lot of stuff in semantic space (Open Graph, likes, Facebook Connect), etc. I would not be too focused on semantic thing. It belongs to solution space, not to problem space.