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.
Search engine. A search engine is a software program or script available through the Internet that searches documents and files for keywords and returns the results of any files containing those keywords. Today, there are thousands of different search engines available on the Internet, each with their own abilities and features.