Here is a simplification of my layout:
You should set z-index to absolutely positioned div that is greater than to relative div.
Something like that
Content of unknown length
Content of unknown height
z-index sets layers positioning in depth of page.
Or you may use floating to show all text of unkown length. But in this case you could not absolutely position your div
Content of unknown length Content of unknown length Content of unknown length Content of unknown length Content of unknown length Content of unknown length Content of unknown length Content of unknown length
Content of unknown height