RevCMS | Register | Gender choose?

I'm working on a new RevCMS Skin for my Retro and I'd like to have a gender choose while register in it but it dosen't work :/

How it looks like:
http://www.bilder-upload.eu/upload/0...1425203870.png

Code:

PHP Code:

---

<table width="100%">
                                <tr>
                                    <td valign="bottom"><div id="boy_tab" class="tab-active"><img src="app/tpl/skins/HabBlue/img/icon_boy.png" alt="boy" /></div></td>
                                    <td rowspan="2"><img id="look" src="app/tpl/skins/HabBlue/img/avatar_boy.png" alt="" /></td>
                                </tr>
                                <tr>
                                    <td><div id="girl_tab" class="tab"><img src="app/tpl/skins/HabBlue/img/icon_girl.png" alt="girl" /></div></td>
                                </tr>
                            </table>
                        <script type="text/javascript">
                            $('#boy_tab').click(function() {
                                this.className = 'tab-active';
                                document.getElementById('girl_tab').className = 'tab';
                                document.getElementById('look').src = 'app/tpl/skins/HabBlue/img/avatar_boy.png';
                                document.getElementById('gender').value = 'm';
                            });

                            $('#girl_tab').click(function() {
                                this.className = 'tab-active';
                                document.getElementById('boy_tab').className = 'tab';
                                document.getElementById('look').src = 'app/tpl/skins/HabBlue/img/avatar_girl.png';
                                document.getElementById('gender').value = 'f';
                            });
                        </script>
                        <input type="hidden" name="reg_gender" id="gender" value="m" /> 


---

What it should do (I think you already know): if you click for example on the girl icon it should show you a girl avatar and let you register as a girl.

What it does: nothing.

It worked with another Skin I've made some time ago :/