In general, don't use anything on the drawing toolbar.
Lines, arrows rectangles, shapes all use VML graphics which use absolute
positioning, and are only visible in IE5.5 on Windows.
Most of the web components are safe. The database components depend on your
server - must be Windows, others require FP2002 extensions.
Setting FrontPage to accommodate Netscape actually turns off some features
that Netscape can handle, or which will fail gracefully in Netscape. NN4
users (according to the stats.) amount to about 2% of users in the browser
wars. The other Netscape versions can do whatever IE can do (except VML
graphics and the marquee - and NN7 can use the marquee). It is a question
of compromise - maximise the featureset or maximise the audience, and how
far back in ancient browsers do you design for?
If you restrict the site to IE5.5 users and above (about 80% of users), use
anything on the drawing toolbar. If you want the other 20%, don't use that
toolbar.
I've never used Dreamweaver - never got through the learning curve. In my
opinion graphics should be done in a graphics program, use a tool designed
for the job.
Rectangles and lines can be constructed with tables, cell borders and other
HTML tricks in conjunction with CSS.
With experience and testing in different browsers you will learn what will
work, what will fail.
And if there is a problem, ask in this newsgroup.