var f=document.getElementById('fade');
var opacity=0;
setOpacity(f,opacity);
setTimeout(fadein,100);

function fadein() {
  var f=document.getElementById('fade');
  setOpacity(f, opacity);
  opacity+=10;
  if (opacity < 100) 
      setTimeout(fadein,100);
}

function setOpacity(obj, opacity) {
  opacity = (opacity == 100)?99.999:opacity;
  // IE/Win
  obj.style.filter = "alpha(opacity:"+opacity+")";
  // Safari<1.2, Konqueror
  obj.style.KHTMLOpacity = opacity/100;
  // Older Mozilla and Firefox
  obj.style.MozOpacity = opacity/100;
  // Safari 1.2, newer Firefox and Mozilla, CSS3
  obj.style.opacity = opacity/100;
}