function popup(u, w, h, n, s, r, ext){
	var janela;
	var topo 	= (screen.availHeight - h) / 2;
	var esq 	= (screen.availWidth - w) / 2;
	var scrl 	= (s) ? 'yes' : 'no';
	var red 	= (r) ? 'yes' : 'no';
	janela = window.open (u, n, 'width=' + w + ', height=' + h + ', top=' + topo + ', left=' + esq + ', scrollbars=' + scrl + ', resizable=' +  red);
	janela.focus();
}