Formatting Sites - Page Width
This Web Site has a width of 800 pixels, which is ideal for what are best described as 'technical' or 'professional' sites.
If it was a general-interest Web Site then you might use 720 or even 640 pixels. Only use an undefined width if you don't want any width at all.
Note that only the Home Page is shown at this width.
The only trouble with fixed-width Web Sites is that they do tend to print badly. That is why, BodgeIt! can generate a special width and menu-free print page for printing.