[jQuery] how to uncheck the checked checkedboxs

[germacran]

hi

i write the following to uncheck the checked checkedboxs

<script src="jquery-1.2.6-intellisense.js" type="text/javascript"></
script>
     <script language="javascript" type="text/javascript">
        $("document").ready(function(){
        $("#Button1").click(function(){
       alert($(":checkbox[checked='checked']").length);
        });

        });
    </script>

but do nothing !!

any help?

thanks in advance.