determining tallness an html list boldly filled

i pull plans html. positioning structure looks this:

  <div id='hostdiv'>
    <div id='backgrounddiv'>
     ... sketch credentials ...
    </div>
    <div id='foregrounddiv' style='position: absolute;'>
     ... sketch forehead ...
    </div>
  </div>

the forehead contains list component boldly populated text, hence quarrel heights competence change depending volume calm going cell.
how i envision final tallness list component foregroun? i need information set repremand tallness background. there proceed pre-render list javascript review out the height? trick?

ps. distance hostdiv competence change browser resizes.