Doesn't work in DW -- shocked, so shocked... No wait, not shocked... what's the opposite of shocked? grounded?
Given that half the pages I've ever written can be loaded into that steaming pile of manure, you hit 'save', and now it's broken; OH NOES, it doesn't work in Dreamweaver, NOT THAT!?!?
You want split view, open the text editor, make it half the screen width, open a browser, make it half the screen width... Win 7 makes that REALLY easy with it's "drag off the side to make it half width".
Do yourself a favor, burn the manuals, make microwave art out of the DVD, and forget that bloated overpriced nube predating scam even exists. As a dearly departed friend of mine often said, "the only thing about Dreamweaver that can be considered professional grade tools are the people promoting it's use."
Though I'd suggest ditching the universal reset since that's going to shtup you on forms, don't make it an accessibility train wreck with the fixed width layout, avoid declaring widths on everything... and WHY do you have the HTML CDATA escape wrapping a second copy of your CSS in the external file? Or more specifically the second reset -- AHA! you're running the universal reset TWICE - That could be causing your problems right there. When you call it before the NAV ones you are undoing all the margins and padding above it!