Well, there are a few items to note...
(Just my $.02)
First, ditch dumbweaver n' frontpage. Don't trust apps that add in their own code in order to trick-boink it into workin'. You'll waste a lot of time debuggin' it.
Second, in your source, there is a mix of relative layout and fixed position method uses within the box model. A carry-over from excessive table layout use.
Lastly, try these references...
Zeldman
A List Apart
w3c tutorials
...and to help understand what those css attributes actually mean, try
Select Oracle
Hope this helps.