Do not click on this advertisement!
Here is a screenshot:
If you click on the advertisement you may end up at a web site hosting Exploit.HTML.IframeBof and Trojan-Downloader.JS.Multi.av.
We can safely view the target web page by using a web sniffer. When we do that we discover that a couple of lines of code have been added to insert an iframe that loads content from two different chinese URLs.