Do ads contain a virus:
Ads can sometimes contain
evil (or at least rude) program code that hijacks your web browser to try to
fool or coerce you into doing something. This is usually something the web site
itself doesn't want, but when there are so many ads to manage it's hard to
police every single one of them. When you do encounter one of these ads, do the
web site a favor and report it so they can do something about it.