janela = function(url,titulo,w,h,scrol){
	lado = (w >= screen.width) ? 0 : (screen.width-w)/2;
	cima = (h >= screen.height) ? 0 : (screen.height-h)/2;
	if(cima >= screen.height-38) cima = screen.height-38;
	if(cima < 0) cima = 0;
	if(lado < 0) lado = 0;
	conf='width='+w+',height='+h+',top='+cima+',left='+lado+',scrollbars='+scrol+',status=1';
	window.open(url,titulo,conf);
}