function positionWindow(width, height)
{    
    var screenWidth = screen.width; //determines screen width
    var screenHeight = screen.height; //determines screen height
    
	xpos = (screenWidth - width)/2;
    ypos = (screenHeight - height)/2;
    window.moveTo(xpos,ypos);  
    window.resizeTo(width,height);
}

//addEvent() by John Resig
function addEvent( obj, type, fn ){ 
   if (obj.addEventListener){ 
      obj.addEventListener( type, fn, false );
   }
   else if (obj.attachEvent){ 
      obj["e"+type+fn] = fn; 
      obj[type+fn] = function(){ obj["e"+type+fn]( window.event ); } 
      obj.attachEvent( "on"+type, obj[type+fn] ); 
   } 
}

function removeEvent( obj, type, fn ){ 
   if (obj.removeEventListener){ 
      obj.removeEventListener( type, fn, false );
   }
   else if (obj.detachEvent){ 
      obj["e"+type+fn] = fn; 
      obj[type+fn] = function(){ obj["e"+type+fn]( window.event ); } 
      obj.detachEvent( "on"+type, obj[type+fn] ); 
   } 
}