[AbbyK9]

It's the advertisements that I would be worried about - they are the most likely cause for warnings such as this popping up.

If you are running Firefox as your browser, you can install the add-on AdBlockPlus, which disables all advertising, both static and pop-up on websites, so you would not have to worry about virus-containing ads anymore. Plus it's so much nicer to browse when you don't see all sorts of annoying ads.