We reported yesterday that some iPhone 4 users have claimed to have a yellow discoloration located beneath the screen. Today a member of the Apple Insider Forums explains the reasoning behind this along with a solution, waiting it out!
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.
Source: AppleInsider.com