function selectIntroClass() 
{
    var noClasses = 5;
    var randomClassSuffix = Math.floor(Math.random() * noClasses) + 1;

    document.getElementById('home-intro').className = 'home-image-'+randomClassSuffix;
}

if (window.addEventListener)
{
    window.addEventListener("load",selectIntroClass,false);
}
else if (window.attachEvent)
{
    window.attachEvent("onload",selectIntroClass);
}

/*
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(selectIntroClass);

*/