Quarto website treats `h1` as `quarto-title-block` if no `title` in frontmatter

[simonsteiger]

Bug description

Hello,

After updating to 1.6.39, quarto websites began treating a raw html h1 as the page title, which appears to drop any other CSS attached to said h1.

Maybe this behaviour is intended; it came as a surprise for me at least.

Steps to reproduce

Here's the example that caused the error.

Setting title to "" (or removing it from the frontmatter entirely) causes "upper-content" class to be overridden by quarto's title block.

---
title: "test" # works
# title: ""   # doesn't work
---

```{=html}
<div class="upper-content">
    <h1>Turing.jl</h1>
</div>
```

And the corresponding styles.css:

.upper-content {
    color: red;
}

Expected behavior

The words "Turing.jl" should show up in red.

Actual behavior

The words "Turing.jl" show up in black (CSS class "upper-content" was not applied).

Your environment

• I ran quarto preview on the terminal
• MacOS Sequoia 15.1.1

Quarto check output

Quarto 1.6.39
[✓] Checking environment information...
      Quarto cache location: /Users/simonsteiger/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.6.39
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (external install)
      Chromium: 869685

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /Users/simonsteiger/Library/TinyTeX/bin/universal-darwin
      Version: 2023

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.11.6
      Path: /opt/homebrew/opt/python@3.11/bin/python3.11
      Jupyter: 5.5.0
      Kernels: julia-1.11, julia-1.10, julia-1.8, julia-1.9

      NOTE: No Jupyter kernel for Python found

[✓] Checking R installation...........OK
      Version: 4.3.2
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/library
      knitr: 1.43
      rmarkdown: 2.23

[✓] Checking Knitr engine render......OK

[mcanouil]

What is your goal when doing raw h1 and no title? (Why not set and target the title?)

Anyhow, this is a duplicate:

• h1 is converted to title in page header if no title is provided in the yaml #11618
• top-level H1 should become titles when no other title is provided as metadata #11660

(In the future, please search for related issues before opening a new one)

[simonsteiger]

We used <h1> in addition to a custom CSS class to create an animated banner for the landing page (see https://turinglang.org/pr-previews/105/). We did not want to style other titles in the same way, so we did not target the title.

Sorry for not searching better previously!