Preview the page in a browser - as that is what everyone else will be doing
when it is published on the Web.
WYWIWYG is only an approximation of what you will see, since the great
variation in computer systems, configurations, screen types, video cards,
screen resolutions, browsers and operating systems do not guarantee that
everyone will see what you see.
What You See Is What You Might Get If You're Lucky is more appropriate
description......(!).
Frontpage is not a word processor. It has less flexibility over formatting
than Word does, and takes a bit of work to get what you want exactly right,
and takes some understanding of the way HTML works. It will take a bit of
trial and error to get it right.
Can you post the URL to the page, so we can see what might be wrong? We
can't really diagnose the problem without a look at the page, but I suspect
that because Preview Mode is not strictly a browser, this might have
something to do with it.