On the whole, most of the web sites
are positioned centrally within the browser window these days. You will
come across very few full-screen (liquid) or left-aligned / fixed-size,
as it was a few years back.
Why a central layout is good
The "2.0" style is uncomplicated,
bold and straightforward. The websites that sit straight front
& center have a simpler, bolder and honest feel.
Moreover, as we are being more
reasonable with our pixels (and content), we are not under pressure to
stuff a lot of information above the waterline/fold.
We're using less to say more, so we
can be a bit more free and easy with the amount of space used, and pad
out our content with lots of lovely white space.
When & how to use a central
layout
I would recommend you to lay out your
site on the center unless there is really good reason why you should
not.
You may be wanting to get more
creative with the space, or get as much information on-screen as
possible.