function rendVisible(){
document.getElementById("idElement").setAttribute("class", "visible");
}
function rendInvisible(){
document.getElementById("idElement").setAttribute("class", "invisible");
}

function visibilite(thingId){
var targetElement;
targetElement = document.getElementById(thingId) ;
if (targetElement.style.display == "none")
{
targetElement.style.display = "" ;
} else {
targetElement.style.display = "none" ;
}
}