// function Voltar ao Topo

function backtotop()

{

  var x1 = x2 = x3 = 0;

  var y1 = y2 = y3 = 0;

  

  if(document.documentElement)

  {

    x1 = document.documentElement.scrollLeft || 0;

    y1 = document.documentElement.scrollTop || 0;

  }

  

  if(document.body)

  {

    x2 = document.body.scrollLeft || 0;

    y2 = document.body.scrollTop || 0;

  }

  

  x3 = window.scrollX || 0;

  y3 = window.scrollY || 0;

  

  var x = Math.max(x1, Math.max(x2, x3));

  var y = Math.max(y1, Math.max(y2, y3));

  

  window.scrollTo(Math.floor(x / 2), Math.floor(y / 2));

  

  if(x > 0 || y > 0)

  {

    window.setTimeout("backtotop()", 25);

  }

}