history.pushState - not working?

I want to change html without reload. I do it like:

$('#left_menu_item').click(function(e) {
    if (!!(window.history && history.pushState)) {
        e.preventDefault();
        history.pushState(null, null, newUrl);
    }
});

It works correctly. But if I want to go back with "Back" button - browser change url on previous, but it not reload page. Why?