function change_main_image (mainname, from) {
                var oldimg="";
                var newimg="";

                var oldimgsrc="";

                oldimg=document.getElementById(mainname);
                newimg=document.getElementById(from);
                oldimgsrc=oldimg.src;
                oldimg.src=newimg.src;
                newimg.src=oldimgsrc;
                return false;
}