How Do I Post Images on Craiglist Properlly?

I know how to post images on craiglist but when I do the image looks some what pixely and distorted. here an example of an image I made that I tried to post as an example of my logo work http://img862.imageshack.us/img862/9755/hotdish.png , the exact same image is saved on my computer but when I post it on craiglist it looks all messed up. Is there a way I can save the image that will make it look better when I post it? thank you