janela = function(url, titulo , w, h, scrol) {
	lado=(screen.width)?(screen.width-w)/2:100;
	cima=(screen.height)?(screen.height-h)/2-28:20;
	if(lado<0) lado = 0;
	if(cima<0) cima = 0;
	conf='width='+w+',height='+h+',top='+cima+',left='+lado+',scrollbars='+scrol+',status=1';
	return !window.open(url,titulo,conf);
}