function AbreJanela(url, altura, largura, top, left)
{
  top=((top/2)-(altura/2));
  left=((left/2)-(largura/2));
  window.open(url, altura, 'toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=no, menubar=no, top='+top+', left='+left+', width='+largura+', height='+altura);
}
//javascript:AbreJanela('arquivo.php',400,630,window.screen.availHeight, window.screen.availWidth)