Note that many websites have their own advertising, unrelated to adware.
GPSTool adds a BHO to Internet Explorer.
This application may show various types of advertising, not limited to pop-up ads. These include ads from auction sites, adult sites, etc.
An Interesting fact with this Adware is, this one looks for Keywords "Date/Sex/Adult" , on any open html page and hyperlinks it.
The appended url to this hyperlink is http://<Something>/cgi-bin/v30/ezlclk.fcgi? .
These are search pages with search keyword being "Date/Sex/Adult". This follows up by a wide range of popups ranging anything (most of the times popups like adult sites, casino sites, False malware scans etc).
When clicked on this hyperlink , it leads to lot of other popups.