function popup(url,width,height,yesno) {
	var left 	= (screen.width-width)/2;
	var top 	= (screen.height-height)/2;
	
	newwindow=window.open(url,'','height='+height+',width='+width+',top='+top+',left='+left+',resizeable='+yesno);
	if (window.focus) {newwindow.focus()}
}