Misery loves company. I'm relieved to learn that I am not the only one who has experienced this troubling problem. After spending a lot of time today trying to figure out what I did wrong to make my ads disappear, I have concluded that the iWeb AdSense widget does not work. I corrected the problem on my web site by using the iWeb html widget. All you have to do is create new ads within Google AdSense and copy the html code to the html frame you drag onto your web page from the widget panel. Click on Apply. It might take several minutes for ads to appear on your pages in iWeb and in your browser (after re-publishing your site). As others have mentioned, you can customize your ads and even create a whole new palette, if you wish, using the Google AdSense ad design tool. I do wish, however, that Apple would fix this iWeb glitch. The AdSense widget is (was) very convenient to use.