All you need to keep the wrapper_bottom from getting over lapped or moved to the side is "clear:both;" applied to the wrapper_bottom div.

This creates a new problem, however, that your wrapper_middle and wrapper_middle_main div's (and applied graphics) don't enlarge with the extended pad_md div. Considering your know how, I trust you know how to fix that.

-SDPETERSEN
Mohican Web Ware