I have recently been reading a lot of questions from people who have just been getting in to web design, who wonder why their websites look different on various screens.
The main reason why this is the case is because these sites are designed to fit a "fixed width".
These widths are written in pixels, which means that any screen which has a wider width in pixels, will cause your site too look bad, as you will be left with a large amount of white space.
So you may be wondering what you could do to prevent your pages from looking different on various screens.
The best thing to do is to use a percentage in stead of PX. This will mean that your page will re-size to fit a particular percentage of the users browser window and so will look a lot better.