From time to time, when I browse the internet , after entering a site's URL , I get a warning message that a pop up has been blocked , then a question mark and a set of numbers appends itself after the URL.

It doesn't matter what site I want to navigate to, it can be a site I have developed, a well know site like drupal.org for instance. Here's what happens:

    enter url:  example.com
    warning: pop up blocked
    url change to: example.com/?1347628900

After checking the pop up ( which of course turns out to be an unwanted ad ), i deducted that the request and the pop up were linked.

This has never happened to me before, I'm not sure how this got started, how can I get rid of this? Clearing the cache , cookies etc... doesn't solve the issue.

I'm using a Macbook Pro OS10.6.7 , Chrome 13.0.782.24 beta.

Thanks in advance for any tips!