Forum Moderators: not2easy
You can force a minimum width for the content container by setting a CSS min-width on Opera and Mozilla/Firefox, and use a hack to deliver a width: to Internet Explorer (which does not recognize min-width). This will force the layout to occupy a certain horizontal distance, so smaller screens will see a horizontal scrollbar.
But IMHO, a better solution is to make your design more fluid, so it is not as resolution-dependent.