There have been reports of iPhone 4s suffering from odd screen discoloration, in the form of yellow or brown splotches near the edges. There’s a chance that these problems may right themselves. According to a poster on the AppleInsider Forums, this just means the glue hasn’t dried yet, and it will fix itself with a bit of time:
Apple is using a bonding agent called Organofunctional Silane Z-6011 to bond the layers of glass. Apparently, Apple (or more likely Foxconn) is shipping these products so quickly that the evaporation process is not complete. However, after one or two days of use, especially with the screen on, will complete the evaporation process and the yellow “blotches” will disappear.How do I know? I was involved in pitching Z-6011 to Apple.
If true, then this issue might just go away on its own.
I too have the yellow discoloration on the bottom of my new iphone 4 screen.
I called Apple and they guy told me that it is residue from the manufacturing process and that they rushed the shipments out to hit deadline. He also told me that its just because the residue is not dry fully yet and it should clear up within a couple of days.