If you're one of the millions of people who does some occasional Web browsing while at work, chances are sooner or later you're going to click on something you probably shouldn't. In most cases, you don't know what you're getting into until it's too late--a situation developer Pratham Kumar (maker of the now defunct 2View) has solved with a small and simple Firefox extension called No-NSFW (download).
Once installed it will give you the heads-up every time you mouse over a link. You'll get a small warning in the lower right hand corner of your browser that either marks it safe (SFW) or not safe (NSFW) with color coding to match. If someone hasn't voted on a page, it's simply left unrated.
Other people with the extension curate the ratings. To vote on a site you're on, you just need to click the small eyeglass button right by where the warnings pop up and mark the page. Each time users vote on a page, those votes are tallied up--a number that will shift with the tide of its safety rating.
The extension works with both Firefox 2 and the latest beta of Firefox 3.