< iframe id="rotate_sites" src="" width="600" height="850" frameborder="1">
</iframe>
< script>
var websites = 1,
    sites =['http://mpets.mobi','http://mpets.mobi'];
function newSite() {
    if ( websites >= sites.length ) {
        websites = 0;
    }
    document.getElementById('rotate_sites').src = sites[websites];
    websites++;
}
setInterval(newSite, 2000);
< /script>