Icon compatability

Hi,
could someone point me to the right catagory for learning about compatability? I've made an icon from a dvd cap that I drew on from my dvd drive installed in the puter then copied into a new doc and did my layers and text and saved as a jpg. But when I upload it the image won't show just a blank white box with the red x in it.
Any ideas?
thanks in advance for any information.
j