Changes in Interface
On 1 November 2011, Google rolled out an official redesign of its interface that "simplified" the look of Gmail into a more minimalist design to provide a more consistent look throughout its products and services as part of an overall design change. Users were able to preview the new interface design and beta-test for months prior to the official release as well as revert to the old interface until 27 March 2012, when Google discontinued it.
Read more about this topic: Gmail Interface