Remove claim that the Link header is semantically equivalent to the HTML link element

[jfhr]

…TML <link> element

Description

The Link header is not equivalent to the <link> element. This PR would change "semantically equivalent" to "In many cases, it has the same effect as".

Motivation

While this statement was part of RFC 5988, it has been removed in the superseding RFC 8022.

This was discussed at the time:

[the link header field] is semantically equivalent to the element in HTML, as well as the atom:link feed-level element in Atom.

No, it's not; an application has to opt into using the link header field.

In particular, the rel values for the Link header are defined by the IANA Link Relations registry, and the rel values for the <link> element are defined by the HTML5 spec with extensions defined in the microformats wiki.

Additional details

For example, this works:

<link rel="stylesheet" href="index.css">

but this doesn't:

Link: <index.css>; rel="stylesheet"

(it works in Firefox, but it isn't standardized and webkit declined to implement it)

Related issues and pull requests

Relates to #24870

[github-actions]

Preview URLs

• /en-US/docs/Web/HTTP/Headers/Link

[estelle]

Thanks! 🎉