It turns out this happened before with the [net neutrality banner](https://meta.stackexchange.com/a/298295/295232). The banner has received some updates so the script is different this time. In time, I'll write something that uses cross-domain storage to remember if you have dismissed the banner once (as opposed to dismissing it always, even before you see it the first time):

```js
// ==UserScript==
// @name        Stack Exchange Dismiss Announcement Banner
// @namespace   https://github.com/Glorfindel83/
// @description Automatically dismisses an announcement banner whenever you visit a (new) site.
// @author      Glorfindel
// @version     0.1
// @match       *://*.stackexchange.com/*
// @match       *://*.stackoverflow.com/*
// @match       *://*.superuser.com/*
// @match       *://*.serverfault.com/*
// @match       *://*.askubuntu.com/*
// @match       *://*.stackapps.com/*
// @match       *://*.mathoverflow.net/*
// @grant       none
// ==/UserScript==

(function () {
  "use strict";
  setTimeout(function() {
    $("div#announcement-banner a.js-dismiss").click();
  }, 100);
})();
```