iPhone safari borked my blog layout

I noticed yesterday that iPhone safari is making my top image bar go all wonky. The rest of the page looks fine just the header is messed up (the background image appears stretched strangely). It works fine on the desktop safari (and firefox, and IE, etc) so I don’t know what’s causing it.

Before I begin to dig into the problem does anyone out there in the intertubes have any idea why it’s doing this?