img3_on = new Image(32,24);
img3_on.src="../images/fdroite1.gif";
img3_off = new Image(32,24);
img3_off.src="../images/fdroite.gif"; 

img4_on = new Image(32,24);
img4_on.src="../images/fgauche1.gif";
img4_off = new Image(32,24);
img4_off.src="../images/fgauche.gif";

function over_image(parm_name)
    {
        document[parm_name].src = eval(parm_name + "_on.src");
    }
function off_image(parm_name)
    {
        document[parm_name].src = eval(parm_name + "_off.src");
    }