function JS_change_image(){
    $$('.blockbtnproduit').each(function(el,i){
	el.addEvent('mouseover',function(e){
	    e.stop();
	    $$('#grdimgaccueil img').set("src",el.get('rel'));
	});
    });
}

window.addEvent('domready',function(){
    JS_change_image();
})