CMS Made Simple Forums

I am new to CMS, so apologies for dumm questions.
We tryn to make a ebsite with a horizontal drop down menu, that worls ok, but the menu comes in between the heading and the sidebar + content part, We would like however the menu to be overlaying the header with a transparent background.The menu should be positioned at the right bottom of the header.
Any suggestions on how to achieve this?

transparency in firefox: -moz-opacity:.8;

in IE: filter:alpha(opacity=80);