A few days ago, we spotted Twitter’s initial roll out of a geolocation feature on its Website. It appeared that Twitter was testing the feature because it quickly turned it off. Last night, the feature went back on, and Twitter co-founder and CEO Biz Stone officially announced it.

While Twitter’s geolocation feature has been live through its API since last November, this is the first time Twitter has enabled geolocation on its site. To start Tweeting with your location attached, you need to enable the feature in your Twitter Account Settings. Once you’ve opted-in, you will be able to add your location information to all your Tweets or choose to add them to individual Tweets as you compose them. You can choose to share your exact location (your coordinates) or your neighborhood or town.

Currently, the feature only works with Firefox 3.5 and Chrome for Windows. If you decide you want to send a Tweet without your location, you can simply click the “x” next to your location to disable it. Interestingly, if you Tweet with your geolocation on Twitter, the location doesn’t seem to show up in TweetDeck, Seesmic or presumably other third-party clients. And It doesn’t work from Twitter’s mobile site, at least not on the iPhone, where it would make more sense.

As we wrote in our earlier coverage, the timing of this move by Twitter is purposeful. With the SXSW conference in Austin starting today, the location wars are heating up. Earlier in the week, the New York Times reported that Facebook would unveil its answer to location next month at its f8 conference. Google, meanwhile, is in the game with Latitude and to some extent Buzz (but could have been in it a lot more). And of course, Foursquare, Gowalla and a host of other location-based apps are rolling out additional functionality. As we previously noted, many of these apps use Twitter’s geolocation API to pass the data back to Twitter, so it makes sense that this would be a good time to turn the functionality on for the website.