[hỏi] tham số ?t=2017.08.11.1 đằng sau các file css có tác dụng gì

(function(t, n, e) {
    "use strict";
 
    function i(n, e) {
        this.element = n, this.options = t.extend({}, o, e), this._defaults = o, this._name = a, this.init()
    }
    var a = "pusher",
        o = {
            watch: "a",
            initialPath: n.location.pathname,
            before: function(t) {
                t()
            },
            handler: function() {},
            after: function() {},
            fail: function() {
 
                toastr.error('Lá»—i hoặc Ä‘ang xĂ¢y dá»±ng')
            },
            onStateCreation: function() {}
        };
    i.prototype = {
        init: function() {
            var e = this;
            if (history.pushState) {
                var i = r({
                    path: e.options.initialPath
                }, e.options.onStateCreation);
 
                history.replaceState(i, null, i.path), t(e.element).on("click", 'a[rel="async"]', function(n) {
                    n.preventDefault();
                    var i = r({
                        path: t(this).attr("href"),
                        elem: t(this)
                    }, e.options.onStateCreation);
                    s(e, i, !0)
                }), n.addEventListener("popstate", function(t) {
                    s(e, t.state)
                })
            }
        }
    };
    var r = function(t, n) {
            var e = {};
            return t = t || {}, e.path = t.path, e.time = (new Date).getTime(), n && n(e, t.elem), e
        },
        s = function(n, e, i) {
            if (e) {
                var a = {
                        state: e,
                        get: function(t) {
                            return u(a.res, t)
                        },
                        updateText: function(n) {
                            var e = t(n);
                            this.get(n).each(function(n) {
                                var i = t(this).text();
                                e.eq(n).text(i)
                            })
                        },
                        updateHtml: function(n) {
                            var e = t(n);
                            this.get(n).each(function(n) {
                                var i = t(this).contents();
                                e.eq(n).html(i)
                            })
                        }
                    },
                    o = function() {
                        t.ajax({
                            type: "GET",
                            url: e.path
                        }).done(function(t) {
                            a.res = t, i && history.pushState(e, null, e.path), n.options.handler.apply(a)
                        }).fail(function() {
                            n.options.fail.apply(a)
                        }).always(function() {
                            n.options.after.apply(a)
                        })
                    };
                n.options.before.apply(a, [o])
            }
        },
        u = function(n, e) {
            var i = t("<root>").html(n),
                a = i.find(e);
            return a
        };
    t.fn[a] = function(n) {
        t.data(e, "plugin_" + a) || t.data(e, "plugin_" + a, new i(this, n))
    }
})(jQuery, window, document);
$(document).pusher({
    handler: function() {
        this.updateText("title");
        this.updateHtml("#mainContent");
        this.updateHtml("#loadJS");
    }
});