ACRONYM Versus ABBR

Two tags for shortened words, and the one HTML kept is the one Internet Explorer refused to support.

In 2026: Partly. ACRONYM still renders and still shows its title on hover, exactly like ABBR, but HTML5 made it obsolete and kept ABBR. The joke is the history: IE supported ACRONYM and not ABBR, so authors used the tag that worked, and the web filled with acronym elements wrapping things that are not acronyms. IE7 finally supported ABBR in 2006 and the argument ended.

Where it came from: HTML 4.0, W3C, 1997, defined both. Internet Explorer supported ACRONYM from version 4 and ABBR only from version 7 in 2006, which decided a decade of markup.
MDN ↗HTML 4.01 ↗

<p>Hover these:</p>
<p style="font-size:1.2em">
  <acronym title="North Atlantic Treaty Organization">NATO</acronym> is in the dead tag.
  <abbr title="HyperText Markup Language">HTML</abbr> is in the living one.
</p>
<p style="font:13px Verdana">Both show a tooltip. Browsers render the two
identically, which is exactly why HTML5 kept only one.</p>