disable back button

gistfile1.js

(function (w) {
        w.location.hash = '#no-back';

        var historyApi = (typeof w.history.pushState !== 'undefined');

        if (w.location.hash == '#no-back') {
            if (historyApi) {
                w.history.pushState(null, '', '#stay');
            } else {
                w.location.hash = '#stay';
            }

            function hashChanged() {
                if (w.location.hash == '#no-back') {
                    if (historyApi) {
                        w.history.pushState(null, '', '#stay');
                    } else {
                        w.location.hash = '#stay';
                    }
                }
            }

            if (w.addEventListener) {
                w.addEventListener('hashchange', hashChanged, false);
            } else if (w.attachEvent) {
                w.attachEvent('onhashchange', hashChanged);
            }
        }
    })(window, document);