rel="shortcut icon"

The two word rel that gave every website a face and every server a log full of favicon.ico 404s.

In 2026: Partly: the link below is honoured by every browser but you cannot see it work in this frame, because a frame's icon, like its title, never reaches the tab. IE5 invented the whole thing in 1999 and also invented asking every server for /favicon.ico uninvited, which servers have been answering or 404ing ever since. The conforming rel today is just icon; shortcut is a fossil browsers still swallow because the old web says it constantly.

Where it came from: Internet Explorer 5, 1999, for the Favorites menu. HTML5 standardised rel=icon; the shortcut prefix survives as a legacy token browsers must accept.
Wikipedia ↗MDN rel ↗

<link rel="shortcut icon" href="https://xbawx.com/favicon.ico">

<p style="font:13px Verdana">This frame declared the icon below as its favicon.
The tab shows nothing, a frame's icon never reaches it, so here is the file
itself, fetched the way IE5 started fetching it in 1999, by just asking:</p>
<p><img src="https://xbawx.com/favicon.ico" width="32" height="32"
        style="image-rendering:pixelated;background:#333;padding:6px;border:1px solid #999"
        alt="This site's favicon"></p>