on 06-13-2013 02:41 PM
1. Use a browser with a popup blocker.
even better ...
2. Run FULL malware scans on your computer! It is probably infected.
on 06-13-2013 02:55 PM
Are you talking about pop-ups or advertisements?
The window that appears, such as the Browse feature for uploading images or the Enlarge feature on listings, those are pop-ups.
You can't stop eBay from advertising on their own web site, but if you receive intrusions from third parties, you can stop that practice.
Install and run Malwarebytes:
And, there are several web browsers that won't allow advertising. Firefox with the Ad Block Plus add-on works well.