PSA ad on default page

[waiman39hk]

Start from yesterday my site default page is showing PSA ads. The link is something like:
www.xyz.com/stock

But if I enter the complete url to the default page, the targeted ads show up again. ie.
www.xyz.com/stock/index.htm

Can anyone explain to me why would this happen?

[sandpetra]

I've only seen this happen to my locally stored pages I preview using my browser (Preview - ie - before I've uploaded them to the site)