This site browses the 4927 emails from Really Good Emails to count the use of certain HTML and CSS features. The numbers on this page indicate the percentage of HTML emails that use the corresponding HTML or CSS feature at least once.
Data is updated every month.

HTML Percentage
<tr>
 96.59022%
<td>
 96.26548%
<table>
 96.00162%
<a>
 94.68236%
<img>
 90.0345%
<div>
 85.75198%
<br>
 82.22042%
<span>
 77.877%
<tbody>
 66.18632%
<style>
 65.57743%
<head>
 58.61579%
<meta>
 58.35194%
<body>
 56.22082%
<p>
 54.08971%
<title>
 50.11163%
<center>
 43.45443%
<html>
 36.02598%
<strong>
 34.92998%
<h1>
 19.05825%
<xml>
 16.82565%
<o:pixelsperinch>
 16.82565%
<o:officedocumentsettings>
 16.64299%
<o:allowpng>
 16.60239%
<em>
 16.05439%
<h2>
 15.4861%
<link>
 14.87721%
<b>
 12.60402%
<th>
 12.1778%
<v:textbox>
 11.85305%
<v:rect>
 11.69068%
<v:fill>
 10.39172%
<h3>
 10.29024%
<hr>
 10.10757%
<font>
 9.86401%
<w:anchorlock>
 7.89527%
<li>
 7.08342%
<ul>
 6.6572%
<v:roundrect>
 6.35275%
<u>
 5.5206%
<h4>
 4.60727%
<i>
 4.22164%
<sup>
 3.16623%
<input>
 2.61823%
<label>
 2.49645%
<section>
 2.41526%
<v:image>
 1.86726%
<h5>
 1.48163%
<small>
 1.46134%
<thead>
 1.13659%
<v:background>
 1.13659%
<blockquote>
 0.97422%
<ol>
 0.95393%
<h6>
 0.93363%
<source>
 0.93363%
<nobr>
 0.83215%
<custom>
 0.81185%
<form>
 0.71037%
<footer>
 0.66978%
<picture>
 0.66978%
<header>
 0.58859%
<map>
 0.50741%
<area>
 0.48711%
<strike>
 0.40593%
<pre>
 0.40593%
<video>
 0.38563%
<media_query_styles>
 0.30444%
<o:p>
 0.28415%
<button>
 0.26385%
<singleline>
 0.26385%
<main>
 0.24356%
<code>
 0.20296%
<no>
 0.20296%
<address>
 0.20296%
<v:shape>
 0.18267%
<unsubscribe>
 0.18267%
<nav>
 0.16237%
<s>
 0.16237%
<figure>
 0.16237%
<article>
 0.14207%
<wbr>
 0.12178%
<time>
 0.12178%
<base>
 0.10148%
<v:shapetype>
 0.10148%
<ins>
 0.10148%
<sub>
 0.10148%
<noscript>
 0.10148%
<figcaption>
 0.08119%
<left>
 0.08119%
<raw>
 0.08119%
<tfoot>
 0.08119%
<col>
 0.08119%
<g>
 0.08119%
<multiline>
 0.08119%
<column>
 0.08119%
<colgroup>
 0.06089%
<option>
 0.06089%
<select>
 0.06089%
<bdo>
 0.06089%
<audio>
 0.06089%
<a:textbox>
 0.06089%
<doctype>
 0.06089%
<o:allowjpg>
 0.04059%
<cite>
 0.04059%
<caption>
 0.04059%
<i18n-string>
 0.04059%
<selector>
 0.04059%
<a:roundrect>
 0.04059%
<field>
 0.0203%
<bodycopy>
 0.0203%
<webversion>
 0.0203%
<tr_>
 0.0203%
<abbr>
 0.0203%
<v:oval>
 0.0203%
<divre>
 0.0203%
<eloqua>
 0.0203%
<pstyle="text-align:>
 0.0203%
<thea>
 0.0203%
<dviv>
 0.0203%
<cq:include>
 0.0203%
<layout>
 0.0203%
<svg>
 0.0203%
<rect>
 0.0203%
<circle>
 0.0203%
<spanonlin>
 0.0203%
<script>
 0.0203%
<big>
 0.0203%
<amp-anim>
 0.0203%
<i-amphtml-sizer>
 0.0203%
<amp-img>
 0.0203%
<amp-accordion>
 0.0203%
<xml:namespace>
 0.0203%
<ampscript>
 0.0203%
<repeater>
 0.0203%
<choice>
 0.0203%
<f>
 0.0203%
<aside>
 0.0203%
<textarea>
 0.0203%
<mj-text>
 0.0203%
<style-type="text/css">
 0.0203%
<module>
 0.0203%
<modulezone>
 0.0203%
<editable>
 0.0203%
<canvas>
 0.0203%
<intro-directions>
 0.0203%
<foo>
 0.0203%
<mj-raw>
 0.0203%
<assign>
 0.0203%
<emsp>
 0.0203%
<v:shadow>
 0.0203%
<tablewidth="100%"border="0"cellspacing="0"cellpadding="0"background="">
 0.0203%
<o:officedocumensettings>
 0.0203%
<del>
 0.0203%
<ptdashes>
 0.0203%
<noplaintext>
 0.0203%
<legend>
 0.0203%
<iframe>
 0.0203%
<fieldset>
 0.0203%
<en>
 0.0203%
<span.bold>
 0.0203%
<text>
 0.0203%