Just 15 months after introducing a "new Twitter," the social networking site is undergoing another major redesign.

Twitter announced today that it's rolling out a simplified design with the goal to make Twitter "easier than ever" to use. 

The redesign will unify the look and feel of Twitter, whether you're using it on the Web, a mobile phone or Tweetdeck, a desktop app acquired by Twitter earlier this year. It will put an emphasis on five activities that you can toggle between: (1) Home, (2) Connect, (3) Discover, (4) Me, (5) Tweet.

Media such as photos and videos will be embedded into the Home stream and #hashtags are played up with the Discover tab.

One of the most noteable changes for those who use Twitter often is that the left and right columns are swapping. Tweets will now appear on the right, with user info, lists, "who to follow" and trends on the left. 

GigaOm's Colleen Taylor writes that the redesign gives Twitter a more "mainstream" feel, though Forbes contributor Robert Hof wonders if it could mean more ads are on the horizon.

You can get the new version of Twitter on your iPhone here or Android here. It will be gradually rolling out to Twitter users.

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