// ==UserScript==
// @name        OldRedditinterface
// @namespace   https://www.reddit.com/
// @description Change reddit intrface
// @version     1
// @include     *://*.reddit.com/*
// @run-at      document-start
// @grant       none
// @noframes
// ==/UserScript==

var url = window.location.href;

if( url.indexOf( "www.reddit.com" ) !== -1 )
{   
    var res = url.replace("www", "old");
    window.location.replace( res );
    return;
}