function book()
{
    document.getElementById('book').style.display = (document.getElementById('book').style.display == 'block' ? 'none' : 'block');
    document.getElementById('book').style.visibility = (document.getElementById('book').style.visibility == 'visible' ? 'hidden' : 'visible');
}
function bookpap()
{
    document.getElementById('bookpap').style.display = (document.getElementById('bookpap').style.display == 'block' ? 'none' : 'block');
    document.getElementById('bookpap').style.visibility = (document.getElementById('bookpap').style.visibility == 'visible' ? 'hidden' : 'visible');
}
function sous_menu()
{
    document.getElementById('sousmenu').style.display = (document.getElementById('sousmenu').style.display == 'block' ? 'none' : 'block');
    document.getElementById('sousmenu').style.visibility = (document.getElementById('sousmenu').style.visibility == 'visible' ? 'hidden' : 'visible');
}
function montre(id) {
if (document.getElementById) {
document.getElementById(id).style.display="block";
} else if (document.all) {
document.all[id].style.display="block";
} else if (document.layers) {
document.layers[id].display="block";
}
}

function cache(id) {
if (document.getElementById) {
document.getElementById(id).style.display="none";
} else if (document.all) {
document.all[id].style.display="none";
} else if (document.layers) {
document.layers[id].display="none";
}
}