It's the buttons at the top that are making it too wide. Try reducing the font size on those buttons a little bit. One thing that will help you is when you are doing the final fitting change your screen resolution to 800x600 and make sure it looks good on that. That is what the majority of users are running these days and if it looks good at 800x600 it will most likely look fine higher. I design my pages for 800x600 but make sure they will work ok at 640x480 (sometimes very hard to do) and also test at 1024x768.