function opaq(id){
val=75 // en %
document.getElementById(''+id+'').style.opacity=val/100 //firefox opéra safari
document.getElementById(''+id+'').style.MozOpacity=val/100 //ancien firefox
document.getElementById(''+id+'').style.KhtmlOpacity =val/100 // konqueror
document.getElementById(''+id+'').style.filter="alpha(opacity="+val+")" // IE
}
function rest(id){
val=50 // en %
document.getElementById(''+id+'').style.opacity=val/100 //firefox opéra safari
document.getElementById(''+id+'').style.MozOpacity=val/100 //ancien firefox
document.getElementById(''+id+'').style.KhtmlOpacity =val/100 // konqueror
document.getElementById(''+id+'').style.filter="alpha(opacity="+val+")" // IE
}