var window_is_opened;

function popup() {
	if ((window_is_opened == true) && (pop.closed == false)) {
		pop.focus();
	}
	else {
		pop = window.open('intro.html','mizani','width=800,height=600,scrollbars=yes');
    	pop.moveTo(0,0);
    	pop.resizeTo(window.screen.availWidth,window.screen.availHeight);
    	pop.focus();
    	window_is_opened = true;	
	}
}