function img_on(id_name) {
        var name, tmp;
        name=document.getElementById(id_name).src;
        tmp=name.substr(name, name.length-5)+'.jpg';
        document.getElementById(id_name).src=tmp;
    }
    function img_out(id_name) {
        var name, tmp;
        name=document.getElementById(id_name).src;
        tmp=name.substr(name, name.length-4)+'a.jpg';
        document.getElementById(id_name).src=tmp;
    }