The jQuery Ajax example I showed in class didn't work with IE. It turns out that it's due to IE's (rather aggressive) caching behavior. Adding a "cache: false" to the .ajax call fixed the problem:

$(function(){
    $('#clickBtn').click(function(){
        $.ajax({
            url: 'A1',
            success: function(data){ $('#number').html(data); },
            cache: false
        });
    });
});