Do all of your formatting on your image first. Then save as 600 pixels. Images don't load here if the file size is too large, and basenjiforums.com doesn't seem to format the image for you. If you're getting negative images and odd colours then it may be your image formatting software. Try again! I'd love to see your card.
Please would someone tell me how not to put up a photo in negative - the purple should be green, the blue is the white of the Basenjis except where its yellow !
What file format are you using? Best to use .jpg, and as others have said, downsize it to something reasonable. If it looks normal on your computer as a .jpg or .jpeg, it should display fine on the forum.