Hi Wesing,
We would needs some more information in order to resolve this issue.
1) Please let me know what browser do you use and what is the version of your browser.
2) Do you see this issue always or does this happen intermittently.
3) What threads you where browsing when you saw this issue.
4) Is it possible for you to get me a screenshot of the ad.doubleclick.net urls that you see in your browser back button.
If you can provide us wiht the above information it can help us in resolving the issue.
Thanks,
Ibadmin - Quiltingboard Admin