It’s been a while since I had to deal with this issue, so I may be a little wobbly on the details, but this is what it boiled down to when I ran into a similar problem. iPhones are non-standard in their handling of CSS pixels vs device pixels. Screen resolutions improve (and vary significantly) so a “pixel” isn’t a standard size. I think that the new iPhones report their device width in portrait mode as something like 1024px. For most browsers on most devices, the difference between “device pixels” and “CSS pixels” isn’t really an issue. It’s compensated for. Apple, however, has a whole … thing about their screen resolution and therefor is a pain in the ass about it.