Users will have different sized monitors, different browsers and different platforms. Check your designs on different set-ups to see what it will look like and how it will be displayed. Appearance - the final concern. Appearance, though the last concern, is extremely important on the internet. Too much empty space will give the impression that you have nothing to say.
Organization has to be more than just an impression.
It has to be logical to the end-user. As a website designer you have a responsibility to the end-users. They aren't just hits, they are user experiences. Everytime end-users come to your site they are experiencing the internet through your design.