What does these errors mean?

Technical Q&A

Topic summary

A user is encountering HTML validation errors on their Shopify website (japanfoodgrocer.com) when using the W3C validator. The errors relate to the CSS container-type property.

Issue identified:

  • The container-type property is from CSS Containment Module Level 3
  • Not all browsers support this property yet
  • Modern browsers (Chrome, Edge 105+, Firefox) do support it

Current status:

  • User confirms they’re using an updated Chrome browser
  • Unresolved question: User cannot locate where this CSS code exists in their Shopify theme files
  • User is asking how to access or modify the CSS Containment Module Level 3 code

The discussion remains open with the technical issue of locating and fixing the specific CSS code in Shopify still unanswered.

Summarized with AI on November 2. AI used: claude-sonnet-4-5-20250929.
1

I am trying to validate my HTML code using https://validator.w3.org/ and I am coming up with the following errors

JapanFoodGrocer_0-1737481116908.png
JapanFoodGrocer_0-1737481116908.png618×103 5.28 KB

Can anybody help me with finding a solution to clear this error.

My website is https://www.japanfoodgrocer.com/

2

Hi @JapanFoodGrocer ,

This is a property from the CSS Containment Module Level 3, and currently, not all browsers support it.

The container-type property is supported in modern browsers such as Chrome, Edge (version 105 and above), and Firefox. If you are using an older browser version, please consider updating it for better compatibility.

Hope this can help!

Best,

Daisy

3

I am using Chrome and it is updated. However I cannot find where the code is at in my Shopify code to fix the error. How do get access to the CSS Containment Module Level 3?