function tablet_foren(id) {


document.getElementById("windows_foren").style['display'] = 'none';
document.getElementById("android_foren").style['display'] = 'none';
document.getElementById("weitere_foren").style['display'] = 'none';
document.getElementById("apple_foren").style['display'] = 'none';

document.getElementById("navi_windows").className = '';
document.getElementById("navi_android").className = '';
document.getElementById("navi_weitere").className = '';
document.getElementById("navi_apple").className = '';
document.getElementById("navi_"+id).className = 'active';

document.getElementById(id+"_foren").style['display'] = '';
}