removed experimental note for nested H1 and added to 140 CSS Removal

[dletorey]

Description

• Removed experimental note for Remove UA styles for H1
• Added Firefox 140 release note > CSS Removal for 39629 Remove UA styles for H1

Motivation

• Work on Issue #39629

Additional details

• Checked that the removal has happened in:
  • Firefox Beta 140.0b6
  • Firefox nightly 141.0a1

Related issues and pull requests

• N/A

[github-actions]

Preview URLs

• /en-US/docs/Mozilla/Firefox/Experimental_features
• /en-US/docs/Mozilla/Firefox/Releases/140

External URLs (77)

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox

• https://bugzil.la/1057233 (1 time)
• https://bugzil.la/1099557 (1 time)
• https://bugzil.la/1190623 (1 time)
• https://bugzil.la/1223880 (1 time)
• https://bugzil.la/1225110 (1 time)
• https://bugzil.la/1280613 (1 time)
• https://bugzil.la/1312588 (1 time)
• https://bugzil.la/1318984 (1 time)
• https://bugzil.la/1391243 (1 time)
• https://bugzil.la/1461589 (1 time)
• https://bugzil.la/1467846 (1 time)
• https://bugzil.la/1539075 (1 time)
• https://bugzil.la/1602129 (1 time)
• https://bugzil.la/1617609 (1 time)
• https://bugzil.la/1676779 (1 time)
• https://bugzil.la/1676791 (1 time)
• https://bugzil.la/1687364 (1 time)
• https://bugzil.la/1697647 (1 time)
• https://bugzil.la/1734997 (1 time)
• https://bugzil.la/1736914 (1 time)
• https://bugzil.la/1737918 (1 time)
• https://bugzil.la/1737920 (1 time)
• https://bugzil.la/1750902 (1 time)
• https://bugzil.la/1754897 (1 time)
• https://bugzil.la/1794475 (1 time)
• https://bugzil.la/1794628 (1 time)
• https://bugzil.la/1804573 (1 time)
• https://bugzil.la/1807685 (1 time)
• https://bugzil.la/1808410 (1 time)
• https://bugzil.la/1809005 (1 time)
• https://bugzil.la/1817303 (1 time)
• https://bugzil.la/1823463 (1 time)
• https://bugzil.la/1838746 (1 time)
• https://bugzil.la/1853418 (1 time)
• https://bugzil.la/1855763 (1 time)
• https://bugzil.la/1867058 (1 time)
• https://bugzil.la/1884424 (1 time)
• https://bugzil.la/1884425 (1 time)
• https://bugzil.la/1886134 (1 time)
• https://bugzil.la/1886441 (1 time)
• https://bugzil.la/1888729 (1 time)
• https://bugzil.la/1889561 (1 time)
• https://bugzil.la/1891446 (1 time)
• https://bugzil.la/1900929 (1 time)
• https://bugzil.la/1901037 (1 time)
• https://bugzil.la/1905706 (1 time)
• https://bugzil.la/1906301 (1 time)
• https://bugzil.la/1917783 (1 time)
• https://bugzil.la/1917784 (1 time)
• https://bugzil.la/1920115 (1 time)
• https://bugzil.la/1931290 (1 time)
• https://bugzil.la/1934683 (1 time)
• https://bugzil.la/1950759 (1 time)
• https://bugzil.la/1951772 (1 time)
• https://bugzil.la/1953557 (1 time)
• https://bugzil.la/1954685 (1 time)
• https://bugzil.la/1963263 (1 time)
• https://bugzil.la/1964077 (1 time)
• https://bugzil.la/502258 (1 time)
• https://bugzil.la/558594 (1 time)
• https://bugzil.la/778617 (1 time)
• https://bugzil.la/917755 (1 time)
• https://bugzil.la/918189 (1 time)
• https://bugzilla.mozilla.org (1 time)
• https://drafts.csswg.org/css-inline/ (1 time)
• https://en.wikipedia.org/wiki/Graphics_Processing_Unit (1 time)
• https://github.com/mozilla/explainers/tree/main/archive/ppa-experiment (1 time)
• https://jpeg.org/jpegxl/ (1 time)
• https://support.mozilla.org/en-US/kb/about-config-editor-firefox (1 time)
• https://support.mozilla.org/en-US/kb/privacy-preserving-attribution (1 time)
• https://w3c.github.io/ppa/ (1 time)
• https://wiki.mozilla.org/Origin_Trials (1 time)
• https://www.mozilla.org/en-US/firefox/channel/desktop/ (3 times)
• https://www.mozilla.org/en-US/firefox/developer/ (2 times)
• https://www.mozilla.org/en-US/firefox/new/ (1 time)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/140
Title: Firefox 140 for developers

• https://bugzil.la/1964922 (1 time) (Note! This may be a new URL 👀)
• https://github.com/whatwg/html/pull/7829 (1 time) (Note! This may be a new URL 👀)

[dipikabh]

For more clarity, should we begin this update with first stating what's been removed?
And then explain what the previous behavior was doing. WDYT about:

Suggested change

- The `<h1>` heading doesn't decrease in font size now when nested within [sectioning elements](/en-US/docs/Web/HTML/Guides/Content_categories#sectioning_content) `<article>`, `<aside>`, `<nav>`, and `<section>`. The UA styles for `<h1>` nested within sectioning elements are no longer relevant since the outline algorithm [has been removed](https://github.com/whatwg/html/pull/7829) from the HTML specification. ([Firefox bug 1964922](https://bugzil.la/1964922)).

- The UA styles for `<h1>` elements nested within [sectioning elements](/en-US/docs/Web/HTML/Guides/Content_categories#sectioning_content) have been removed, following the [removal of the outline algorithm](https://github.com/whatwg/html/pull/7829) from the HTML specification. Previously, the `<h1>` headings nested within `<article>`, `<aside>`, `<nav>`, and `<section>` would appear smaller. Now, `<h1>` elements have a consistent font size, regardless of the nesting. ([Firefox bug 1964922](https://bugzil.la/1964922)).