I only just noticed this, and this is true for BOTH my old iPhone 4 and my new iPhone 4S. Using the default wallpapers that came with the phone, there is no dark grey bar along the bottom where the dock is, as can be seen in the first picture below. In the 2nd pic however, using a picture I took from my iPhone 4, there is clearly a dark grey line across the bottom. The grey line is ONLY there on the home screen, and not there when I open any apps. So I can only assume it's a background issue... Is anyone else experiencing this or might know why? I've tried searching here and on Google but did not turn up any results. Also, there is a VERY tiny thin line that you can see on the very bottom of both screenshots. I assume this is normal and on every phone? Any advice/suggestions would be appreciated, thanks!