<script type="text/javascript">
var compte = 100;
var interv = setInterval(setopacity, 100);
function setopacity() {
compte = compte - 1;
document.getElementById("gmess").style.opacity=compte;
if (compte == 0) {
clearInterval(interv);
} else {
var interv = setInterval(setopacity, 100);
}
}
</script><div style="background: #ff0000" id="gmess">sdsd</div>