// image roll
//------------------------------------*/
function imgRoll(obj,flag) {
    var pathsrc = obj.getAttribute("src");
    var path = pathsrc.slice(0,pathsrc.lastIndexOf("/")+1);
    var imgname = pathsrc.slice(pathsrc.lastIndexOf("/")+1,pathsrc.length);
    if(flag) {
        var imgname = imgname.replace(/_off/i,"_on");
    } else {
        var imgname = imgname.replace(/_on/i,"_off");
    }
    obj.setAttribute("src",path + imgname);
}