sfHover = function() {
    var listElements = document.getElementById("menu").getElementsByTagName("LI");
    for (var i=0; i<listElements.length; i++) {
      listElements[i].onmouseover=function() {
        this.className+=" sfhover";
      }
      listElements[i].onmouseout=function() {
      this.className=this.className.replace(new RegExp(" sfhover\\b"), "");
      }
    }
}

var isMac = (navigator.userAgent.indexOf("Mac") != -1);

// Seems to work on everything
if ( isMac ) {
    window.onload=sfHover;
} else {
    // Works on everything but Mac IE
    if (window.addEventListener) {
        window.addEventListener("load", sfHover, false);
    } else if(window.attachEvent) {
        window.attachEvent("onload", sfHover);
    }
}