The width of pages displayed in a browser depend on many
things (screen resolution, font size setting on the
browser ... small/medium/large, whether or not anything
else takes up horizontal space like a favorites listing)
but basically it comes down to the "viewport".
The viewport is that number of horizontal pixels devoted
to displaying the contents of the web page. It is not
merely the width of your computer screen.
For this reason, when you are working in Front Page to
design pages, it is best to preview your pages using
Preview in browser rather that just Preview.
There are a numbers of things you can do to attempt to
keep your pages as consistent as possible. The first and
most important is to use Tables to set up the layout of
your page. The second is to NOT use the space bar or so-
called absolute positioning as a layout tool.
Website design involves much trial and error. You should
test out your site on various browsers (as each works a
little bit different), try various screen resolutions and
font size settings.
This topic has been covered many times in this newsgroup.
I would suggest you take some time to read what others
have said on this topic.