var isNS4=(document.layers) ? 1 : 0;
    var isIE4=(document.all)? 1 : 0;
    var isMoz=((document.getElementById) && !(isIE4)) ? 1 :0;
    
    function hide_layer(slayer) 
    {
      var layer=get_layer(slayer) ;
    
    	if(layer==null){
    		return;
    	}
  		layer.style.visibility = "hidden";
    }
    
    function show_layer(slayer) {
      var layer=get_layer(slayer) ;
  		layer.style.visibility = "visible";
    }
    
    function move_layer_to(slayer, x, y)
    {
      var layer=get_layer(slayer) ;
    	layer.style.left = x;
    	layer.style.top  = y;
    }

    
    function get_layer(name)
    {
      if (isIE4){
    		return document.all[name];
    	} else if (isMoz) {
    		return document.getElementById(name);
    	}
    	return null;	
    }
    
    function modify_content_layer(slayer,content)
    {
      var layer=get_layer(slayer) ;
    	layer.innerHTML=content;
    }