Improved Tool
I created a new, better tool to analyze digital images. It's also free and web based. It features error level analysis, clone detection and more. You should try it right now.
Open Forensically
Image error level analysis is a technique that can help to identify manipulations to compressed (JPEG) images by detecting the distribution of error introduced after resaving the image at a specific compression rate. You can find some more information about this tequnique in my blog post about this experiment and in this presentation by Neal Krawetz which served as the inspiration for this project. He also has a nice tutorial on how to interprete the results. Please do not take the results of this tool to seriously. It's more of a toy than anything else.