OK, 10 out of 10 for the obvious, but it would appear that some web sites that host naughty content are again delivering malware.
According to SANs Institute’s Internet Storm Centre, and highlighted on The Register, visitors to certain sites using Internet Explorer are leaving the pages with more than a smile on their face. A flaw in something called the Vector Markup Language (VML) contained in IE allows spyware to be downloaded and installed on unsuspecting fun seekers PCs.
Solution? Until it is fixed consider using FireFox or Opera. Or the newsagents.