Timeline for Pages arrived February 29, 2012.
TabSite launches a update on March 1, 2012, that accomodates the new Timeline tab app width of 810 pixels!
Related: Update Facebook Timeline Cover Image in TabSite and update 111 x 74 tab app image in TabSite.
Page Admins wanting to create custom tabs at the new 810 px wide size can do so with TabSite.
The TabSite Manager has been extended to allow for the new tab app width of 810 pixels.
By default your current 520 pixel wide content is left justified within the 810 pixel wide area. You can use the "Move Right" button to move your 520 wide content to be centered within the 810 pixel width area. If you haven't upgraded your fan page to use the Timeline, your content should remain left justified.
If you are using the Timeline, you can use the "Move Right" button to center your existing content.
NOTE: For those with custom named tabs (Paid Plan users) you will need to manually update your page tab allowed width to 810 pixels in the Facebook Developer Application settings. See instructions below: