1.1.1 Non-text content

Not everyone can see or process visual information, so make sure you have text to back up all visual shit. Assistive tech can parse text. It can't parse a fucking cat photo or nauseating header video. So maybe add an alt attribute and nuke anything that autoplays (OK that second bit isn't 1.1.1 but seriously, burn that fucker).

See this pile of crap?

<img src="your/fucking/cat.jpg">

Do this instead. Easy.

<img src="your/fucking/cat.jpg" alt="no one thought it was possible to have a bad cat photo, yet here we are.">

WCAG is 22 years old, and missing alternative text for images is still one of the most common failures on the web. It's the first fucking criterion. Fuck.