If you are receiving alot of pop ups when on the net, it is highly likely that you have spyware on your PC. It is not something to worry too much about as:
Everyone has spyware of some form on their PC's at some point.
Kazza (everyone has used it at some point) is littered with Spyware and the newest version of Kazza (2.0 upwards) cannot operate without the SpyWare being active on your PC.
It would be impossible now to browse the net without being hit with some form of SpyWare Trojans etc.
To fight back against the Spyware, Trojans etc....I would recommend everyone to download and run an Anti SpyWare Program. There are a few on the net and I would recommend "SpyBot - Search and Destroy" another good one is "Adware". I've included a link to SpyBot. Simply download the program and once downloaded, install it on your PC and run it. It will scan your PC and delete all your nasty SpyWare. You should run it at least once a week to keep your PC up to speed.
Word of warning to Kazza 2.0 users. If you run SpyBot you will not be able to use Kazza after deleting your Spyware as Kazza 2.0 is SpyWare dependant. Kazza Lite users will be OK as it is still SpyWare Free.
Prevention is always better than a cure. So protect yourselves better with a FireWall. There is a decent free Firewall from ZoneLabs called Zone Alarm. It will run in the background when you are browsing the net and will prevent most Spyware and most if not all Trojans. You can download it free here:
Remember that not all Pop Ups are created by SpyWare. eg This Forum is free and therefore when you enter it you will receive 1 pop-up, so is our password protected page. So please do not instantly think that ever pop-up requires you to reach for your Anti SpyWare Program.