Ich habe ein Problem mit diesem Code für eine Bildschirmtastatur

[beststart]

Hallo, ich weiss, dass dieser Code unvollständig ist. Mein Problem:Wenn man auf den Button 'Alt Gr' klickt, passiert nicht das was passieren soll. Gestern hat aber noch alles funktioniert. Kann mir jemand helfen???

<form name="Keyboard" id="Keyboard">
    <table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <td bgcolor="#C0C0C0">
                <input class="display" name="Display" size="60" />
            </td>
        </tr>

        <tr>
            <td>
                <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td>
                            <input class="input" type="button" value=" 1 " onclick="add('1')" id="eins" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 2 " onclick="add('2')" id="zwei" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 3 " onclick="add('3')" id="drei" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 4 " onclick="add('4')" id="vier" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 5 " onclick="add('5')" id="fuenf" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 6 " onclick="add('6')" id="sechs" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 7 " onclick="add('7')" id="sieben" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 8 " onclick="add('8')" id="acht" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 9 " onclick="add('9')" id="neun" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" 0 " onclick="add('0')" id="null" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" ß " onclick="add('ß')" id="fragez" />
                        </td>
                        <td>
                            <input class="input_r" type="button" value=" &lt;--- " onclick="backspace()" />
                        </td>
                        <td>
                            <input class="input_r" type="reset" value=" RESET " />
                        </td>
                    </tr>
                </table>
            </td>
        </tr>

        <tr>
            <td>
                <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td width="11">
                        </td>
                        <td>
                            <input class="input" type="button" value=" Q " onclick="add('Q')" id="q" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" W " onclick="add('W')" id="w" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" E " onclick="add('E')" id="e" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" R " onclick="add('R')" id="r" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" T " onclick="add('T')" id="t" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" Z " onclick="add('Z')" id="z" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" U " onclick="add('U')" id="u" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" I " onclick="add('I')" id="i" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" O " onclick="add('O')" id="o" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" P " onclick="add('P')" id="p" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" Ü " onclick="add('Ü')" id="ue" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" + " onclick="add('+')" id="plus" />
                        </td>
                    </tr>
                </table>
            </td>
        </tr>

        <tr>
            <td>
                <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td>
                            <input class="input" type="button" value=" A " onclick="add('A')" id="a" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" S " onclick="add('S')" id="s" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" D " onclick="add('D')" id="d" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" F " onclick="add('F')" id="f" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" G " onclick="add('G')" id="g" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" H " onclick="add('H')" id="h" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" J " onclick="add('J')" id="j" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" K " onclick="add('K')" id="k" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" L " onclick="add('L')" id="l" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" Ö " onclick="add('Ö')" id="oe" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" Ä " onclick="add('Ä')" id="ae" />
                        </td>
                        <td>
                            <input class="input_r" type="submit" value=" ENTER " />
                        </td>
                    </tr>
                </table>
            </td>
        </tr>

        <tr>
            <td>
                <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td width="11">
                        </td>
                        <td>
                            <input class="input" type="button" value=" &lt; " onclick="add('&lt;')" id="klals" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" Y " onclick="add('Y')" id="y" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" X " onclick="add('X')" id="x" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" C " onclick="add('C')" id="c" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" V " onclick="add('V')" id="v" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" B " onclick="add('B')" id="b" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" N " onclick="add('N')" id="n" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" M " onclick="add('M')" id="m" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" , " onclick="add(',')" id="komma" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" . " onclick="add('.')" id="punkt" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" - " onclick="add('-')" id="bindestrich" />
                        </td>
                        <td>
                            <input class="input" type="button" value=" groß/klein " onclick="document.getElementById('zwei').value = '&quot;';" />
                        </td>
                    </tr>
                </table>
            </td>
        </tr>

        <tr>
            <td>
                <table border="0" cellpadding="0" cellspacing="0">
                    <tr>
                        <td width="103">
                        </td>
                        <td>
                            <input style="width:233px;" class="input_s" type="button" value=" " onclick="add(' ')" />
                        </td>
                        <td>
                            <input class="input_s" type="button" value=" Alt Gr " onclick="notuse();altgr();" />
                        </td>
                    </tr>
                </table>
            </td>
        </tr>
    </table>
</form>
<script language="JavaScript" type="text/javascript">
//<![CDATA[
  <!--


  function add(Zeichen)
 {
   window.document.Keyboard.Display.value = 
   window.document.Keyboard.Display.value + Zeichen;   
 }
  function backspace() 
{
  document.Keyboard.Display.value = document.Keyboard.Display.value.substring(0,document.Keyboard.Display.value.length-1);
 }
function altgr() 
{
document.getElementById('q').value = '@';
document.getElementById('m').value = 'µ';
document.getElementById('plus').value = '~';
document.getElementById('klals').value = '|';
document.getElementById('zwei').value = '²';
document.getElementById('drei').value = '³';
document.getElementById('sieben').value = '{';
document.getElementById('acht').value = '[';
document.getElementById('neun').value = ']';
document.getElementById('null').value = '}';
document.getElementById('fragez').value = '\';

}
function notuse()
{
document.getElementById('w').disabled=true;
document.getElementById('e').disabled=true;
document.getElementById('r').disabled=true;
document.getElementById('t').disabled=true;
document.getElementById('z').disabled=true;
document.getElementById('u').disabled=true;
document.getElementById('i').disabled=true;
document.getElementById('o').disabled=true;
document.getElementById('p').disabled=true;
document.getElementById('ue').disabled=true;
document.getElementById('a').disabled=true;
document.getElementById('s').disabled=true;
document.getElementById('d').disabled=true;
document.getElementById('f').disabled=true;
document.getElementById('g').disabled=true;
document.getElementById('h').disabled=true;
document.getElementById('j').disabled=true;
document.getElementById('k').disabled=true;
document.getElementById('l').disabled=true;
document.getElementById('oe').disabled=true;
document.getElementById('ae').disabled=true;
document.getElementById('y').disabled=true;
document.getElementById('x').disabled=true;
document.getElementById('c').disabled=true;
document.getElementById('v').disabled=true;
document.getElementById('b').disabled=true;
document.getElementById('n').disabled=true;
document.getElementById('komma').disabled=true;
document.getElementById('punkt').disabled=true;
document.getElementById('bindestrich').disabled=true;
document.getElementById('eins').disabled=true;
document.getElementById('vier').disabled=true;
document.getElementById('fuenf').disabled=true;
document.getElementById('sechs').disabled=true;
}
  //-->
//]]>
</script>