ok = false;
if (navigator.userAgent.indexOf ("Mozilla") != -1) {
  ok = parseInt(navigator.appVersion.substring(0,1)) >= 3
} else {}

if (ok == 1) {
  button1 = new Image(100,100)
  button1.src = "images/accueil.gif"
  button1b = new Image(100,100)
  button1b.src = "images/accueilPut.gif"

  button2 = new Image(100,100)
  button2.src = "images/nosoffres.gif"
  button2b = new Image(100,100)
  button2b.src = "images/nosoffresPut.gif"

  button3 = new Image(100,100)
  button3.src = "images/plansite.gif"
  button3b = new Image(100,100)
  button3b.src = "images/plansitePut.gif"

  button4 = new Image(100,100)
  button4.src = "images/nouscontacter.gif"
  button4b = new Image(100,100)
  button4b.src = "images/nouscontacterPut.gif"

}
function un(nom) {
   if (ok == 1) {
	  if (nom == "b1") {document.b1.src = button1b.src;}
	  if (nom == "b2") {document.b2.src = button2b.src;}
	  if (nom == "b3") {document.b3.src = button3b.src;}
	  if (nom == "b4") {document.b4.src = button4b.src;}
	  
	  return true;
   }
}
function deux(nom) {
   if (ok == 1) {
	  if (nom == "b1") {document.b1.src = button1.src;}
	  if (nom == "b2") {document.b2.src = button2.src;}
	  if (nom == "b3") {document.b3.src = button3.src;}
	  if (nom == "b4") {document.b4.src = button4.src;}

	  return true;
   }
}