var corner_id = 1;
var corner_id_precedent = 1;

function afficherBloc( id_menu ) {
	if (window.document.getElementById(id_menu).style.display == 'block'){
		window.document.getElementById(id_menu).style.display = 'none';
	} else {
		window.document.getElementById(id_menu).style.display = 'block';
	}
}

function changeCorner() {
	window.document.getElementById('corner_image_'+corner_id_precedent).style.display = 'none';
	window.document.getElementById('corner_image_'+corner_id).style.display = 'block';
	corner_id_precedent = corner_id;
	corner_id = corner_id + 1;
	if (corner_id > 2){	corner_id = 1;}
}

setInterval("changeCorner();",4000);