"if the site has being ''hacked'' how can this happen"

Shaneo, I don't know how, and if I did I wouldn't post the details on a forum anyway! Unfortunately the fact is that sites can be hacked. I'm co-administrator of a hobby site which got hacked a few months ago. A virus was piggy-backed to our home page so that unsuspecting visitors, including myself, downloaded it. (my anti-virus program didn't detect it) There are so many nasty things that can be done.

The lesson is, if something looks suspicious get out quick, and never surf without good security.