Over the summer, Gmail pushed out an update. While there are a number of new features designed to increase our productivity that are worth checking out (see What's New in Gmail), you can also opt to return to the classic sites for a limited time only. Google is vague about when they'll eventually phase out the classic view entirely - some sources are projecting the end of October.
If your gmail switched over automatically and you want the old gmail back, go to Settings --> Go back to classic Gmail. Reverting back to the more familiar layout still allows the option to change back to the new version. To do this, simply go back to Settings and click Try the new Gmail.
