When i make banner in fp& then previewing that there come a little red cross on the corner of blank page, why?

i m making a simple website on f.p but having problems in making banner and desired picture adjustment so can somebody help me in making website plzzzzzz!|||That little red "X" is the symbol that means that at the current time, your browser is not supporting the file format. Therefore, your only two options are to 1. try again later, or 2. try a smaller image (fewer bytes), perhaps in a different file format.