Border around application when used in a tiling WM like Ratpoison

[Moult]

Just to keep it on the record, also for the benefit of future users :)

Basically there a border around the entire app, which when hovered over acts as a resize handle. Attempting to resize will not succeed, as it is constrained to the tiling WM (expected behaviour). Screenshot compares it with Firefox. This breaks the user's engagement in the web content.

Would be nice if the border could be removed.