function load_content(data) {
 try {
  xmlhttp = new XMLHttpRequest();
 } catch (w3c) {
  try {
   xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (msie) {
   try {
    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
   } catch (msie_alt) {
    alert("Jetzt haben wir ein Problem");
   }
  }
 }
 xmlhttp.onreadystatechange = change_content;
 xmlhttp.open("GET","sites/" +data, true);
 xmlhttp.setRequestHeader('If-Modified-Since', 'Sat, 1 Jan 2000 00:00:00 GMT');
 xmlhttp.send(null);
}

function change_content() {
 if (xmlhttp.readyState==4) {
  if (xmlhttp.status==200) {
     setOpaque(0);
     setTimeout(fillhtml(), (100*10));
  } else {
   //alert("Jetzt haben wir ein Problem");
  }
 }
}

function fillhtml() {
 document.getElementById("content").innerHTML = xmlhttp.responseText;
 fadein();
}

function fadeout() {
 fader(100,0);
}

function fadein() {
 fader(0, 100);
}


function fader(start, ende) {
 var speed = 15;
 var timer = 0;

 if (start > ende) {
  for (i=start; i >= ende; i--) {
   setTimeout("setOpaque(" + i + ")", (timer * speed));
   timer++;
  }
 } else if (start < ende) {
  for (i=start; i <= ende; i++) {
   setTimeout("setOpaque(" + i + ")", (timer * speed));
   timer++;
  }
 }
}

function setOpaque( val ) {
 var obj = document.getElementById("content").style;
 obj.opacity      = (val/100);
 obj.KhtmlOpacity = (val/100);
 obj.filter       = "alpha(opacity=" + val + ")";
}