function openChat() {
	scr_w=screen.width;
	scr_h=screen.height;
	pptop=(scr_h-450)/2;
	ppleft=(scr_w-780)/2;	
	pop = window.open('chat.php', 'popup_chat', 'width=750,height=550,addressbar=no,directories=no,location=no,menubar=no,resizable=yes,scrollbars=yes,status=no, top='+pptop+', left='+ppleft);
	pop.focus();
}