//function to change zIndex
function change_z_index(obj,z) {
  var obj
  //ie4
  if(document.all) {
    obj=document.all(obj)
    obj.style.zIndex=z
  }
  //ie5,6, Mozilla 1.0 and Opera 6
  if(document.getElementById) {
    obj=document.getElementById(obj)
    obj.style.zIndex=z
  }
  //nn4x
  if(document.layers) {
    obj=document.layers[obj]
    obj.zIndex=z
  }
}