## Why is this an issue?

With the advent of HTML5, many old elements were deprecated. To ensure the best user experience, deprecated elements should not be used. This rule checks for the following deprecated elements:

Element | Remediation Action
--- | ---
`basefont`, `big`, `blink`, `center`, `font`, `marquee`, `multicol`, `nobr`, `spacer`, `tt` | use CSS
`acronym` | use `abbr`
`applet` | use `embed` or `object`
`bgsound` | use `audio`
`frame`, `frameset`, `noframes` | restructure the page to remove frames
`isindex` | use form controls
`dir` | use `ul`
`hgroup` | use `header` or `div`
`listing` | use `pre` and `code`
`nextid` | use GUIDS
`noembed` | use `object` instead of `embed` when fallback is necessary
`plaintext` | use the "text/plain" MIME type
`strike` | use `del` or `s`
`xmp` | use `pre` or `code`, and escape "<" and "&" characters

## Resources

- W3C, Obsolete Features
- WHATWG, Obsolete Features