Warning and error messages in dev tools

[hailiang-shen]

Upon launching jupyter-lab.exe (version 4.1.8), a warning message (screenshot below) appears in dev tools. When I open a notebook file (content below) containing one markdown cell and one code cell, an error message is displayed. The problem seems to be associated with the markdown cell; removing the markdown cell allows the notebook to open without the error message. This occurs in both Edge and Chrome browsers. Despite these warning and error messages, JupyterLab functions properly.

Notebook content is below:
{
"cells": [
{
"cell_type": "markdown",
"id": "f8ac4fdf-c2e8-4ae8-97c9-b72df35bc977",
"metadata": {},
"source": [
"# Test 1\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"id": "48fee351",
"metadata": {
"vscode": {
"languageId": "plaintext"
}
},
"outputs": [],
"source": [
"x = 2\n",
"y = 3\n",
"z = x + y"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "Python 3 (ipykernel)",
"language": "python",
"name": "python3"
},
"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
},
"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3",
"version": "3.10.10"
}
},
"nbformat": 4,
"nbformat_minor": 5
}

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[JasonWeill]

@hailiang-shen Thanks for opening this! It looks like the warning is CSS-related. I'm not sure what the error represents, but another dev can look into this. I appreciate your report.