It would seem that all the problems with the iPhone 4 screen reported by users resolve themselves because the problem is not due to poor assembly or the use of poor quality materials, but to the incompleteness of the phone's manufacturing process. Apple uses certain chemical agents to glue the iPhone 4 screen and the substance used requires a certain period of time to settle properly and, apparently, those yellow spots represent nothing more than a solution that has not yet evaporated properly. Considering that the phone was not left for enough time for that solution to evaporate, there is a possibility that those yellow spots appear on the screen, but after using the phone for a day or 2, they disappear by themselves without leaving any trace.
Some users have reported that the spots on their screens have decreased in size after constant use of the phone, so in the end you don't have to be scared because there is no malfunction of the phone but only a little solution that must evaporate completely.
Apple customer service operators recognized the problem as a technical one and advised users either to wait for the solution to evaporate or to take the phones to the nearest Apple Store to be replaced.
