I'm developing a mobile website and am using an iPhone for testing it. One of the .jpgs used was faulty and displayed as a black rectangle in the iPhone's Safari browser. The code was then changed and there is now a .png image instead. For some reason even after clearing Safaris cache that image is still black, and I need a new phone that has never visited the website before in order to display it correctly.
Why is that happening and how can I fix it?