Check for dead pixels on your iPhone.

<a href="http://www.ipixelcheck.com" title="iPixelCheck" target="_blank"><img src="http://www.modmyi.com/images/apps/ipixelcheck.png" border="0" height="165" width="320" /></a>

<a href="http://www.ipixelcheck.com" title="iPixelCheck" target="_blank">http://www.ipixelcheck.com</a>