Note that many websites have their own advertising, unrelated to adware.
Adware, also known as an Adbot, can do a number of things from profile your online surfing and spending habits to popping up annoying ad windows as you surf. In some cases Adware has been bundled (i.e. peer-to-peer file swapping products) with other software without the user's knowledge or slipped in the fine print of a EULA (End User License Agreement).
Not all Adware is bad, but often users are annoyed by adware's intrusive behavior. Keep in mind that by removing Adware sometimes the program it came bundled with for free may stop functioning. Some Adware, dubbed a "BackDoor Santa" may not perform any activity other then to profile a user?s surfing activity for study.
AdWare can be obnoxious in that it performs "drive-by downloads". Drive-by downloads are accomplished by providing a misleading dialogue box or other methods of stealth installation. Many times users have no idea they have installed the application. Often Adware makers make their application difficult to uninstall.
A "EULA" or End User License Agreement is the agreement you accept when you click "OK" or "Continue" when you are installing software.
Many users never bother to read the EULA.
It is imperative to actually read this agreement before you install any software. No matter how tedious the EULA, you should be able to find out the intent BEFORE you install the software. If you have questions about the EULA- e-mail the company and ask them for clarification. If they cannot clarify this do not install the software.