We've been having serious conversion issues as of late. Our advertising spend has been very high but our ROI has been dead. Doing digging and it was suggested to see what happens when we load our site in a browser that has a third party tool bar installed (pay per view tool bar I was told it is called). What we discovered is on our page load, a different site from the same vertical loads over our site. In addition, our site is framed in banners and copy within our site has added links to exterior offers that are not ours. Is there anything we can do about this?
I'd suggest doing a quick check to see if your site was pharma hacked.. Go to www.example.com/xxx where example is the name of your site and xxx is the name of some popular drugs. It shouldn't be too hard to think of the names.
What you are looking for there is to see if there are pages being generated without your knowledge.
Also, check your google and bing webmaster tools and look at the incoming links. YOu are looking for a lot of odd incoming links . If you see them, then it could be hackers trying to drive people to hacked pages of your site.
Also go through your access logs. Take a look at what is being requested. That will also give you some good hints.