function popup(_link,_w, _h, _scroll)
	{
	if ((_scroll=='') || (typeof(_scroll)=='undefined')) _scroll='no';
	_left=(window.screen.width-_w)/2;
	_top=(window.screen.height-_h)/2;
	_max=(window.screen.height-150);
	if (_h==0)   window.open(_link,'','menubar=no,location=no,scrollbars='+_scroll+',status=no,resizable=no,left=0,top=0,width='+_w+',height='+_max);
			else window.open(_link,'','menubar=no,location=no,scrollbars='+_scroll+',status=no,resizable=no,left='+_left+',top='+_top+',width='+_w+',height='+_h);
	}