/* changement des images du header "Accueil" "Etudiant" "Professionnel" "Journaliste" */
function changeHeader(zone1,zone2,zone3,zone4) {
	var elZone1 = document.getElementById(zone1);
	var elZone2 = document.getElementById(zone2);
	var elZone3 = document.getElementById(zone3);
	var elZone4 = document.getElementById(zone4);
	elZone1.style.display = 'block';
	elZone2.style.display = 'none';
	elZone3.style.display = 'none';
	elZone4.style.display = 'none';
}