var seconds = 20;
var defaultUrl = 'javascript:history.go(-1)';
onload = function () {
    if (defaultUrl == 'javascript:history.go(-1)' && window.history.length == 0) {
        document.getElementById('redirectionMsg').innerHTML = '';
        return;
    }
    window.setInterval(redirection, 1000);
}
function redirection() {
    if (seconds <= 0) {
        window.clearInterval();
        return;
    }
    seconds--;
    document.getElementById('spanSeconds').innerHTML = seconds;
    if (seconds == 0) {
        window.clearInterval();
        location.href = defaultUrl;
    }
}