Most of the people aren’t aware of all the features that Apple integrates into its updates for iPhones. One such feature is zoom in screen. Zoom in feature was added to the 3.x iphone firmware and was available to iPhone 3GS so that they can view bigger icons. However, most of us are not aware about this feature and we accidentally activate it by double tapping three fingers on the screen and then can’t think of what to do and try for a reboot.
To solve this problem just double tap with three fingers again on the springboard. The screen will unzoom and screen will come back to normal size. To deactivate this feature you need to go to Settings/Accessibility and switch off the zoom feature.