function imgGoOver(imgobj) {
    var t = imgobj.src.lastIndexOf("_sel.");
    if (t  >= 0) return;
    var i = imgobj.src.lastIndexOf(".");
    if (i  < 0) return;
    imgobj.src = imgobj.src.substring(0,i) +  "_over" + 
imgobj.src.substring(i);
    return;
}

function imgGoOut(imgobj) {
    var i = imgobj.src.lastIndexOf("_over.");
    if (i  < 0) return;
    imgobj.src = imgobj.src.substring(0,i) + imgobj.src.substring(i+5);
    return;
}

var image1 = new Image();
image1.src =  "immagini/testata_05_over.gif";

var image2= new Image();
image2.src =  "immagini/testata_06_over.gif";

var image3= new Image();
image3.src =  "immagini/testata_07_over.gif";

var image4= new Image();
image4.src =  "immagini/testata_08_over.gif";