var menu1 = document.getElementById('menu1');
var menu2 = document.getElementById('menu2');
var menu3 = document.getElementById('menu3');

function affiche(){
  document.getElementById("sous"+this.id).style.display = "block";
  document.getElementById("sous"+this.id).style.left=document.getElementById(this.id).firstChild.offsetLeft+"px";
  document.getElementById(this.id).firstChild.style.backgroundColor="#772259";
  document.getElementById(this.id).firstChild.style.color="#fff";
}

function masque(){
  document.getElementById("sous"+this.id).style.display = "none";
  document.getElementById(this.id).firstChild.style.backgroundColor="";
  document.getElementById(this.id).firstChild.style.color="#fff";
}

menu1.onmouseover= affiche
menu1.onmouseout= masque
menu2.onmouseover= affiche
menu2.onmouseout= masque
menu3.onmouseover= affiche
menu3.onmouseout= masque