What you see in Dreaweaver is not always what you get in your browsers ... We would need a link and more explanations to help you in the right way ...
For more meaningful answers you'll need to post a URL to your test page so we can see it.
That said, DW Design View is not 100% reliable owing to different browsers, end-user settings and display sizes. Test your site in ALL major browsers (Chrome, FF, IE7, 8, Opera...) with increased/decreased text (zoom, text only). Also test with maximized and smaller than max browser viewport. Do this often during the design phase.
Use valid markup and CSS code. Bad code is the #1 cause of most page rendering problems.