function showSubMenu(id){
  var yOffset = 0;
  var xOffset = -10; // Based on a border of 3px  plus the butlft in the CSS definition
  var widthPadding = 11; // Based on width of button images (butlft and butrgt) in CSS
  var menuElement = document.getElementById(id);
  
  var pos = getElementPos(menuElement.parentNode);
  menuElement.style.top = '230px'; //pos[1] + yOffset + menuElement.offsetHeight + "px";
  menuElement.style.left = pos[0] + xOffset + "px";
  menuElement.style.width = menuElement.parentNode.offsetWidth + widthPadding + "px";
  menuElement.style.visibility="visible";
}

function hideSubMenu(id){
  var menuElement = document.getElementById(id);
  menuElement.style.visibility="hidden";
}

function getElementPos(element) {
   var x = y = 0;

   while (element != null) { // Loop thru parent elements till we get to the top node
     x += element.offsetLeft;
     y += element.offsetTop;
     element = element.offsetParent;
   }
   return [x, y];
}