// random topkey
function random(){
var ramimage = new Array("img/topkey1.jpg","img/topkey2.jpg","img/topkey3.jpg","img/topkey4.jpg");
var dd = new Date();
var sec = dd.getSeconds()
var idx = sec % ramimage.length;
var curimg = ramimage[idx];

document.getElementById("key").style.backgroundImage = "url(" + curimg + ")";
}
random();