Conditional Comments
browser wars 1999 deadA comment that only one browser could see inside.
In 2026: Dead since Internet Explorer 10 dropped support in 2012. Every other browser saw a plain comment, which is what made it the only browser filter that was not a parser bug. The downlevel-revealed form was invalid HTML on purpose.
Where it came from: Microsoft Internet Explorer 5 documentation, 1999. The HTML class pattern is Paul Irish's, 2008. Wikipedia ↗
<!--[if IE]> <p>Any Internet Explorer</p> <![endif]-->
<!--[if IE 6]> <p>Exactly IE 6</p> <![endif]-->
<!--[if lt IE 9]> <script src="html5shiv.js"></script> <![endif]-->
<!--[if gte IE 5.5]> <p>IE 5.5 and up</p> <![endif]-->
<!--[if !IE]> --> <p>Everyone except IE</p> <!-- <![endif]-->
<!-- The pattern that ended up on nearly every page after 2010 -->
<!--[if lt IE 7]> <html class="no-js ie6"> <![endif]-->
<!--[if IE 7]> <html class="no-js ie7"> <![endif]-->
<!--[if IE 8]> <html class="no-js ie8"> <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]-->