When I got a phone and started caring about how things looked on mobile I only fixed some of the pages on my site: home page, blog post template, etc. I have various pages scattered around, however, that I never got around to fixing. Most of why I had been putting this off is that it seemed like a lot of finicky work, like updating the EA forum display was. Except all of these pages are just simple html with no css:

<td>	18462
<tr>	3244
<li>	414
<p>	87
<br>	70
<ul>	61
<i>	51
<head>	31
<html>	31
<th>	31
<hr>	30
<title>	29
<small>	27
<body>	24
<blockquote>	13
<b>	8
<ol>	8
<table>	7
<sup>	6
<strike>	5
<code>	3
<style>	3
<big>	2
<center>	2
<tt>	2
<em>	1
<pre>	1
<script>	1

(Why so many table cells? This list includes my schedule and history which consist of huge tables. Only 5% of the table cells come from the rest of the pages.)

These pages are basically already responsive, and all they needed was:

<meta name="viewport"
      content="width=device-width, initial-scale=1.0">

to tell mobile browsers not to try to display them like a desktop site.