function getElementPosition(elemID) {
    var offsetTrail = document.getElementById(elemID);
    var offsetLeft = 0;
    var offsetTop = 0;
    while (offsetTrail) {
        offsetLeft += offsetTrail.offsetLeft;
        offsetTop += offsetTrail.offsetTop;
        offsetTrail = offsetTrail.offsetParent;
    }
    if (navigator.userAgent.indexOf("Mac") != -1 &&
        typeof document.body.leftMargin != "undefined") {
        offsetLeft += document.body.leftMargin;
        offsetTop += document.body.topMargin;
    }
    return {left:offsetLeft, top:offsetTop};
  }


  function show_ch(id){
    if(document.getElementById('ch'+id)) {
	
	  ch=document.getElementById('ch'+id);
	  pr_pos=getElementPosition('pr'+id);	  
	  pr=document.getElementById('pr'+id);
	  
	  ch.style.left=pr_pos.left+10;
	  ch.style.top=pr_pos.top+pr.offsetHeight;
	  
	  ch.style.display='block';
	}
  }
  
  function hide_ch(id){
    if(document.getElementById('ch'+id)) {
	  ch=document.getElementById('ch'+id);
	  ch.style.display='none';
	}
  }