Requires you to do some arithmetic every time you load a web page, to dissuade compulsive browsing.
Web browsing can be addictive. The compulsive checking of facebook, twitter, news ... you know what I'm talking about. This is my super-simple personal little tool that helped me break my compulsions. All it does is force you to answer a tedious math problem every time you open a new page.
The theory is that, like sipping coffee or dragging on a cigarette, browsing to an appealing web page has instant positive feedback. This extension inserts a tedious step between taking the action to get to the page and the reward. So if you're going to a page, it's because you really want and need to go there. Personally, I have found it effective, and I think you'll feel the psychological difference pretty quickly.
If you don't find it effective ... well, it's free, so just uninstall it.
Incidentally ... while I think the idea is clever, the code is as simple as can be. It could easily be improved upon in a thousand ways, but this was good enough for me.