As per the security advisory (By Microsoft) there is a vulnerability that if a user presses F1 Key on being asked by a Website or webpage, the website can run potentially malicious code or scrip on such computers. That computer can get hacked, information can be stolen or it may also lead to data theft.

All this is applicable only if you are using Windows XP. Other OS from Microspft seems to be safe.

If you don’t press F1 in response, then you won’t have any problem.

The vulnerability exists in the way that VBScript interacts with Windows Help files when using Internet Explorer, read the advisory. If a malicious Web site displayed a specially crafted dialog box and a user pressed the F1 key, arbitrary code could be executed in the security context of the currently logged-on user.