If you're using an image, you just make the image 500px wide and 250px high. If you're using the alternate instructions with the background color, you don't have to do anything, the code will do it for you.
Or I peeked at it just now and there's something about your journal layout that it doesn't like, so yeah pastebin me your code and I'll fiddle with it when I get home and see if I can find a fix for you