function display_img()
{
	var links = document.getElementsByTagName('a');
	var imgcadre = document.getElementById('imgprinc'); 
	for (var i = 0 ; i < links.length ; ++i) {
			links[i].onclick = function() {		
			imgcadre.src = this.href;
			return false;
		};
	}
}
window.onload = display_img;