User Agent style for href hyperlinks and focusable elements

edit 14 June 2026: MathML links were finally not integrated into the first release of MathML Core so corresponding CSS styling was not necessary. However, a new <a> link has been introduced back recently and so UA rules become relevant again. See https://w3c.github.io/mathml-core/#the-a-element

cc @rwlbuis, @bkardell, @emilio

In https://github.com/mathml-refresh/mathml-core/commit/4f34194d9e9be1f0ea679012e4bf2e7b799cde64, I updated a bit the paragraph for href. The suggested style is:

:any-link {
  color: blue;
  text-decoration: none;
}

Chromium's one is:

:any-link {
    color: -webkit-link;
    cursor: pointer;
}

:any-link:active {
    color: -webkit-activelink
}

:-internal-spatial-navigation-interest {
    outline: auto 1px -webkit-focus-ring-color;
    box-shadow: none !important
}

:focus {
    outline: auto 1px -webkit-focus-ring-color
}

WebKit's one is

:any-link {
  color: -webkit-link;
  cursor: auto;
}
:any-link:active {
  color: -webkit-activelink;
}
:focus {
  outline: auto 5px -webkit-focus-ring-color
}

 
Firefox's one is:

:any-link {
    text-decoration: none !important;
 }

We need consistent style.

Read the MathML Core href and focusable-elements sections, starting with the linked commit and the current discussion of the element. Compare the proposed and browser-specific UA rules, then update the specification once a consistent style is agreed; done means the relevant rules are documented consistently for MathML links and focusable elements.