Over the last 30 years man-made CFCs have been the main cause of stratospheric ozone depletion. CFCs however, are not the only ozone-depleting chemicals. Other ODCs include the methylhalides, carbon tetrachloride (CCl4), carbon tetrafluoride (CF4), and the halons which contain bromine instead of chlorine.
Part of the Internet applications glossary: Yahoo! is an Internet portal that incorporates a search engine and a directory of World Wide Web sites organized in a hierarchy of topic categories.
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.