I assume NOF10 produces fixed width pages (as do many wysiwyg page constructors, including the one I use.)
So you either have to accept what it does, or find the option when you get to the site building part, to centre pages (if there is one).
I wouldn't worry so much - some of the biggest and most read web sites are built this way - including the Daily Telegraph, The BBC and Sky TV.
If you post your query in the Web Design section, you may stand a better chance of finding someone who actually uses NOF10.
One problem with web sites that expand to fill evry possible screen width, is that you lose control over exactly where items appear on the page, which is a prime reason that many big sites don't work that way.
You also need to be aware of the screen resolutions that people are likely to view your site with - the commonest by far on the main site I do is 1024 x 768 - so I build my sites to suit that width.