DW rendering is pretty flaky, and generally doesn’t produce results that you will get in any real world browsers. In other words using it as a WYSIWYG tool is pretty much a waste of time IMHO.
Some people rate it pretty highly for text editing and site management, though that’s not my experience.
For best results code by hand (not wysiwyg) and create your design to work in a Mozilla browser (Firefox is best), Webkit (Safari, Konqueror), or Opera (7+) browser, and then fix it for IE/6, and IE5. It’s pretty quick to switch apps and reload a page in a browser.
Try and avoid using tables for layout if you can… you will get far better results and your site will be easier to maintain and upgrade in the long term… plus you’ll learn more about current design practice, rather than using a visual design hack from the 90’s.