var win;

function center(url, winname, winw, winh){
	win = window.open(url, winname, 'width=' + winw + ',height=' + winh + ',status=no');
	var margx = (screen.width - winw) / 2;
	var margy = (screen.height - winh) / 2;	
	win.moveTo(margx, margy);
	win.focus();
}