function positionStart()
{
  var clearButton = document.getElementById("clearcheckboxes");
  if (clearButton)
    clearButton.onclick = clearPositions;
}


function clearPositions()
{
   var checkBoxes = document.getElementsByTagName("input");
   for (var i=0; i<checkBoxes.length; i++)
   {
     if (checkBoxes[i].className = "position" && checkBoxes[i].type=="checkbox")
     {
      checkBoxes[i].checked = false;
     } 
   }  
}