<script src="jQuery/jquery-1.6.2.min.js"></script>
<script>
    $(function(){
        $("#mycheckbox").click(function(){
            var s = $(this).attr("checked");
            alert(s);
        })
    });
</script>
<input type='checkbox' id='mycheckbox' />

        <script src="http://code.jquery.com/jquery-latest.js"></script>
<script>
    $(function(){
        $("#mycheckbox").click(function(){
            var s = this.checked;
            alert(s);
        })
        $("#mybutton").click(function(){
            var i = $("#mycheckbox")[0].checked;    
            alert(i);
        })
    });
</script>
<input type='checkbox' id='mycheckbox' />
<input type='button' id='mybutton' value='按钮' />