Kilotest: Diagnoses of CSS invalid violation by HTML element 0 on Sightline Institute page

Here is how tools diagnose the CSS invalid issue for HTML element 0 of the Sightline Institute page.

Basics

About the CSS invalid issue
- Why it matters: Document cannot be properly displayed
- Priority: high
- Related WCAG standard: 4.1
About the Sightline Institute page
- URL: https://www.sightline.org/
- Tested on 2026-04-03 at 04:04
About HTML element 0
- Tag name: HTML
- Text: [not applicable]
- Start tag: <html lang="en-US">
- XPath: /html
- Bounding box: x = 0, y = 0, width = 1920, height = 3596

CSS: contain-intrinsic-size: Property contain-intrinsic-size doesn't exist.
Tool: Html Checker API (World Wide Web Consortium)
CSS: font-weight: semi-condensed is not a font-weight value.
Tool: Html Checker API (World Wide Web Consortium)
CSS: Parse Error.
Tool: Html Checker API (World Wide Web Consortium)
CSS: display-none: Parse Error.
Tool: Html Checker API (World Wide Web Consortium)
CSS: font-weight: 600px is not a font-weight value.
Tool: Html Checker API (World Wide Web Consortium)