<script language="JavaScript">

function getCookie (name) {
    var dc = document.cookie;
    var cname = name + "=";

    if (dc.length > 0) {
      begin = dc.indexOf(cname);
      if (begin != -1) {
        begin += cname.length;
        end = dc.indexOf("", begin);
        if (end == -1) end = dc.length;
        return unescape(dc.substring(begin, end));
        }
      }
    return null;
}
</script>

<form>
<input type="button" value="Get Cookie Value" onClick="this.form.tf.value = getCookie('myCookie')">
<input type="text" name="tf" size="30">
</form>