<layer> was once a (non-standard) HTML element

[zcorpan]

4.1.2 The layer element

This was once a non-standard HTML element supported in Netscape 4:

https://en.wikipedia.org/wiki/Layer_element

Per https://rainy-periwinkle.glitch.me/permalink/6fc3100b7dece523fa6fd81cc26a2948e82f96a990bd1031961474b6161f9866.html (via https://almanac.httparchive.org/en/2019/markup ) there were 979 pages (0.01848061762639402%) using layer in August 2019 httparchive data set. I don't expect compat problems, but it could be worth checking to verify.