var sfHover = function() {
    var lis = $A($('nav').getElementsByTagName('li'));
    lis.each(function (li) {
        Event.observe(li, 'mouseover', function () {
            this.className='sfhover';
        }.bindAsEventListener(li));
        Event.observe(li, 'mouseout', function () {
            this.className='';
        }.bindAsEventListener(li));
    });
}
Event.observe(window, 'load', function () {
    if (window.navigator.userAgent.match(/MSIE/i))
        sfHover();
});