function change(element) {
ns5 = (document.getElementById)? true:false;
ns4 = (document.layers)? true:false;
ie4 = (document.all)? true:false;

var elementdefaut = 'viet'
var element1 = 'fr'
var element2 = 'eng'
var element3 = 'deutch'


if (ns5) {
    document.getElementById(element1).style.visibility = 'hidden';
    document.getElementById(element2).style.visibility = 'hidden';
    document.getElementById(element3).style.visibility = 'hidden';
    document.getElementById(elementdefaut).style.visibility = 'visible';
    document.getElementById(element).style.visibility = 'visible';
}

if (ns4) {
    eval('document.' + element1).visibility = 'hidden';
    eval('document.' + element2).visibility = 'hidden';
    eval('document.' + element3).visibility = 'hidden';
    eval('document.' + elementdefaut).visibility = 'visible';
    eval('document.' + element).visibility = 'visible';
}

if (ie4) {
    eval(element1).style.visibility = 'hidden';
    eval(element2).style.visibility = 'hidden';  
    eval(element3).style.visibility = 'hidden';  
    eval(elementdefaut).style.visibility = 'visible'; 
    eval(element).style.visibility = 'visible';
}
}
<!-- Script pour déclencher le son -->
function setSndTrack(mp3_file) {
document.getElementById("mediaplayer").innerHTML='<object data="'+mp3_file+'" type="application/x-mplayer2" width="0" height="0"><param name="filename" value="'+mp3_file+'"><param name="autostart" value="1"><param name="loop" value="0"></object>'; 
}