AdWords can be very powerful, if done right. But, according to the article, "Google's AdSense content network can lower your ROI significantly if not done properly."
So, how to do it right? Some tips include:
*using Google's site exclusion tool
*use negative keywords
*write strong ad copy
This article is very valuable, especially if you are new to AdWords or rely on it strongly for your online presence. There is a lot more help out there, but this article will set you off on the right foot.