Google, I know you're doing pretty well right now, but I thought I'd let you in on a little tip that may help you increase your earnings by one millionth of 1%:

If I click the back button, give me the ad that was just on the screen.

Here's the common situation:

I read an email, then click to archive or delete it. While lunging for the archive or delete button, my attention has to go somewhere. It's clearly not on the body of the email since I've mentally put that behind me. So, it often ends up glancing at the AdWords ad running along the top of the page.

I end up clicking either Archive or Delete while at the same time absorbing the text of the ad. By the time I realize the ad may have been of interest to me, I've already clicked Archive or Delete, causing the page to refresh and the ad to go away.

So I hit the back button in an attempt to, well, get back to where I just was. However, I have no such luck.

At the exact moment I find your ads enticing they disappear! And there is no good way to recover them.

I think you may be onto something with this whole pay per click ad thing. However, if I see but don't click on your ads, you don't make money, I feel kind of gypped, and your advertisers don't get my attention.