How to design a webpage that has variable width up to (but not exceeding)a fixed maximum width?

Take a look at the design of the following webpage:
http://www.mozilla.org/products/firefox/

What I like about this is the fact that the width of the page content
varies between about 610 pixels and 830 pixels depending on the size of
the browser window. If you make the browser window smaller or larger,
then the width of the content remains inside aforementioned range.

I recall trying to achieve this a few years ago using just tables and
decided (quietly to myself) that it wasnt possible to do. So I'd love to
know how to do a variable width page but with a capped width. Can anyone
summarise how it's done?

Thanks.

PS: I've just noticed that the above comments do not hold true for
Internet Explorer. It only seems to work with Mozilla Firefox. So bonus
points to anyone that knows a solution that works with all browsers.