There are also programs that run from websites, called trojans (like the trojan horse). They are downloaded along with website content, and when activated, dpwnload the real virus program(s). If the webpage you happen to log onto gets "hacked" (In other words, somene else manages to get into their website setup, and changes it), then just by logging on, you get get infected.

Way too many people take way too many things way too seriously.