var offset_y=20, offset_x=8;

function popis(text){
  var popis=document.getElementById('popis');
  popis.innerHTML=text;

  if(text=="" || text==undefined)popis.style.display="none";
    else popis.style.display="block";
  }


function movemouse(evt){
  var popis=document.getElementById('popis');
  mouseX=(document.uniqueID)?event.clientX:evt.clientX;
  mouseY=(document.uniqueID)?event.clientY:evt.clientY;
  winScrollTop=(window.pageYOffset!=null)?window.pageYOffset:document.body.scrollTop;
  winScrollLeft=(window.pageXOffset!=null)?window.pageXOffset:document.body.scrollLeft;
    
  popis.style.left=winScrollLeft+mouseX+offset_x+'px';
  popis.style.top=winScrollTop+mouseY+offset_y+'px';
  }

document.onmousemove=movemouse;