INTERNET: Find out more how does Google determine which sites are harmful

Some attack sites will try to infect your computer using a “drive-by download,” which automatically seeks out holes in your computer’s defenses and installs badware without any action on your part. Other attack sites will try to trick you into installing badware, frequently by showing fake security alerts or offering free stuff. Once the badware is on your computer, it might steal your passwords or account numbers, send junk email (spam) to others, or try to extort money from you. 

Google then,  scans millions of websites and identifies those that are, or recently were, hosting or distributing badware. If Google later determines a site is clean, they remove the badware warnings.
StopBadware keeps track of sites that Google and others have reported as badware.BY TAATJENE , from StopBadware