Note that many websites have their own advertising, unrelated to adware.
Lop is a group of spyware and hijacker programs that set your Internet Explorer start page and search features to use the site lop.com ('Live Online Portal') or one of its clone sites.
C2.lop is is a pay-per-click search portal where other web sites pay for each click-through to their site via C2.lop. They offer search programs ranging from pornographic material to mp3 downloads. The downside to these programs is of course opening your computer up to advertisements from them and their affiliates. These programs have also been known to install via an Active X control. It also installs a toolbar to your Internet Explorer browser. This toolbar directs you to lop.com sites. Your browser settings are also changed by C2.lop. These changes can take place in your toolbar settings or even your start page through a Browser Helper Object (BHO).
Once installed this program will run whenever Windows is loaded. The value of these autostarters varies from which program you have downloaded for lop.com.