Solution: You can tweak the CSS-output of the xhtml-export by using inline style. The inline style in this solution is inserted via the HTML option of the Textinsert plugin.1) The inline style must be inserted in the //exported// page. Take a look at the wiki code of the pages: :livedemos:iframe-yellow and :livedemos:bgnone.
This IFRAME contains the xhtml export of the page: Default Output
This IFRAME contains the xhtml export of the page: BG-yellow
This IFRAME contains the xhtml export of the page: BG-none
To see how to insert the macros, take a look at the wiki code of the pages: :livedemos:iframe-yellow and :livedemos:bgnone
A LiveDemo for: incorrect table display in xhtml export