function opa_bg_height(id){
  if(id==''){
    var opa_bg=document.getElementsByTagName('div');
  }else{
    var opa_bg=document.getElementById(id).getElementsByTagName('div');
  }
  var skipper=false;
  var max_h=0;
  var skipper1=null;
  for(var i=0;i<opa_bg.length;i++){
    if(opa_bg[i].className.indexOf('background_opa30')>=0){
      var par=opa_bg[i].parentNode;
      var d=par.getElementsByTagName('div');
      d[d.length-1].style.height=d[0].clientHeight+'px';
    }
    if(opa_bg[i].className.indexOf('preview_skipper')>=0){
      skipper=!skipper;
      if(skipper){
        skipper1=opa_bg[i];
      }else{
        skipper1.style.height=max_h+'px';
        opa_bg[i].style.height=max_h+'px';
        max_h=0;
      }
    }
    if(opa_bg[i].className.indexOf('preview_page')>=0&&skipper&&max_h<opa_bg[i].clientHeight){
      max_h=opa_bg[i].clientHeight;
    }
  }
}

function calculate_page_height(){
  var all_divs=document.getElementsByTagName('div');
  var total=0;
  for(var i=0;i<all_divs.length;i++){
    if(all_divs[i].className.indexOf('panel')>=0){
      total+=all_divs[i].clientHeight;
    }
  }
  return total;
}