if you use ms ie this is a MUST read

Microsoft Issues Emergency Security Patch For IE
Microsoft is issuing an emergency patch for a critical Internet Explorer flaw.
JR Raphael, PC World
PC World
Microsoft will issue an emergency security patch Wednesday for all versions of Internet Explorer. The patch is considered a critical fix for the security flaw currently plaguing the IE browser. So far, more than 2 million computers are believed to have been infected.

An advance notification of the patch published Tuesday describes it as protection for a "remote code execution" vulnerability. The move follows Microsoft's security advisory posted last Wednesday and updated Monday explaining the vulnerability and suggesting temporary "workarounds" for protection.

The flaw can be used to let attackers steal personal data such as passwords if a user visits a compromised Web site, of which at least 10,000 are thought to already exist. Thus far, the vulnerability has been used primarily for grabbing gaming passwords for black market sales. The hole could, however, potentially also be used to steal more sensitive information such as banking passwords and other private information. ..........