I mentioned in my review of dict.cc that I loved the ability to turn off ads.
Unfortunately, now that ability is gone. There used to be a large Adsense banner across the top of the page with a link to "Remove Ad". When you clicked the link, the ad would disappear. I guess it used a cookie to remember your preference so that the next time you went to the site, the ads would be gone. Now, there are just ads on the side with no way to hide them.
The ability to disable ads is great from a visitors perspective. People already use adblock software to block ads that they don't want to see and will never click on. Allowing visitors to customize a web site is not only helpful but generous as well. This also solves the dilema of sites which want to make a bit of money but don't want to ruin the experience of their loyal visitors.
On a related note, I'm thinking of bringing back the Adsense ads (with a Remove Ads link) to see how they peform. I had taken them off back in December when I was only making a few cents per week, but my traffic situation has since changed. If anybody has any objections, speak now or forever hold your peace. :)