Recently Peter Köhlmann shared his wisdom about fixed width / flexible width
layouts for web pages. Of fixed width layouts he said:

It is not "bad practice", it is "extremely bad practice"

I saw a similar discussion in another forum... and loved this comment:

Given that an overwhelming majority of major, famous,
often-visited commercial sites have fixed-width layouts, is
it possible to conclude that their designers may know more
than you think they do?

CNN, ESPN, ABC, Microsoft, Dell, Zeldman, Project VII, BBC, A
List Apart, Zen Garden, Adobe, DPreview, even Murray's site,
etc, etc. They all have "incompetent" designers? I seriously
doubt it. I think you need to honestly ask yourself if they
have a very good reason for not sharing your vision.

Poor Peter...

Try not to become a man of success, but rather try to become a man of value.
--Albert Einstein