function popup(url, width, height, lockdown, win_name) { 
	var left	 = (screen.width-width)/2;
	var top		 = (screen.height-(height+110))/2; 
	var lockdown = lockdown === true ? 'scrollbars=0, toolbars=0, statusbar=0, resizable=1, dependant=0, width='+width+', height='+height+', top='+top+', left='+left : '';
	var win_name = win_name != undefined ? win_name : 'popup';
	var win		 = window.open(url, win_name, lockdown);

	if(win.focus) { 
		win.focus();
	}

	return false;
}