If youve ever written a page for the iFrame used on Facebooks apps you’ll know that the width is fixed at 520px.
This in itself isn’t an issue, you can set your page width at the 520 limit and all your content will layout as expected.
Except…. if you exceed the page length and the vertical scroll bar appears. In this case the scroll bar will eat into 20pixels of your carefully designed layout and cause the horizontal scrollbar to show in order to compensate.
Thankfully, this can easily be overcome. If you wrap the page content in the markup below
--Your page goes here --
You can force the horizontal scroll bar not to show. Set your page width to 100% and everything will be layed out as expected!