This is one of the problems you run into when using so much absolute positioning. AP is not really needed to accomplish this layout and it's unfortunate that DreamWeaver steers so many new authors toward using it.
Have a quick look at The Pitfalls of AP
Since you've come this far, there is a sort of fix for you instead of a total re-write. teedoff has you started in the right direction but there is more you will need to do to accomodate all your ap elements.
To center an element you need three things:
- a valid DocType
- an element with a width
- that elements left/right margins set to auto
Make a div that encloses all the elements you want centered.
Make sure that div has a width and that is is wide enough to contain the elements that are inside it. Remember that margins and padding are included when figuring total widths.
Set your new divs left and right margins to auto.
Very important! Since you're using so much ap, you will need to make your new div position relative so your ap elements don't position themselves relative to the body of your document like they are now. You will probably have to adjust the positioning on all of them so they are positioned in their new container correctly.
Hope that all made sense... I can do a quick mock-up for you to follow if it didn't.