var how_many_items = 3;
var now = new Date()
var sec = now.getSeconds()
var item = sec % how_many_items;
item +=1;


if (item==1) {
img="box3a";
}

if (item==2) {
img="box3b";
}

if (item==3) {
img="box3c";
}


document.write('<img src="/images/' + img + '.gif" alt="" />');