are sIFR mouse events expected to work in IE6?

I am using the following code in my sifr.replace() call, with the goal of changing the background on the replaced element.

  onRollOver: function(fi) {
      $(fi.getAncestor()).addClass("over");
  },
  onRollOut: function(fi) {
      $(fi.getAncestor()).removeClass("over");
  }

This works well in in firefox, but not in IE6. I am wondering if I should 开发者_运维技巧look for an error on my part, or if these events are known not to work in IE. Thanks in advance for any thoughts.

Good news: The mouse events do work. My error was in trying to reposition a .png background. IE6 only supports transparent .pngs through the use of a hack (iepngfix.htc in my case), and nobody has managed to make background-position work with such a hack. The workaround was to selectively provide a .gif instead to IE6.