According to the Adwords Blog Google is now evaluating the quality of your landing page
In August, we introduced the Quality Score along with the launch of quality-based minimum bids, letting you know that we evaluate many factors, such as your ad text and clickthrough rate (CTR) to determine the minimum bid for your keyword. Today, we started incorporating a new factor into the Quality Score -- the landing page -- which will look at the content and layout of the pages linked from your ads.
Advertisers who are providing robust and relevant content will see little change. However, for those who are providing a less positive user experience, the Quality Score may decrease and in turn increase the minimum bid required for the keyword to run. To help define site quality, we've created a general set of website design tips and guidelines that should help you evaluate and optimize your site.
You can see landing page guidelines here. Now with all this talk about how important your qualiy score is, it might actually be nice if you Google told you what it was instead of hiding it behind the curtian like it was the Wizard of OZ.