Aha i got it
My original picture (19 KB):
197 x 196 pixels
Your picture (9,6 KB):
150 x 149 pixels
Its nothing wrong with your browser or anything. Wincustomize has an option to select Quality or Performance mode for the page in user profile (if you're registered at Wincustomize). Somehow they have Performance mode only for unregistered users,and thats why image looks ugly. Damn i'm a good detective