Forum der Gemeinschaft Firefox

My page throws errors in Firefox Nightly such as

Expected color but found ‘undefined’. Error in parsing value for ‘background-color’. Declaration dropped. preview.htm:1:1

and

Expected color but found ‘undefined’. Error in parsing value for ‘color’. Declaration dropped. preview.htm:1:1

The page references ten CSS files besides having dozens of its own CSS declarations. The issue is tha the reference provided to the error (:1:1) does not indicate where I can find the error. That is, I don't know which declaration is at fault. Is there some straighforward way to find the declaration in question?

I never feel like webpages scale properly when I visit them. There is always content left off screen or I have to zoom out so much that the text is too small to read. Is there a setting I can change to affect this?

This webpage is particularly egregious: https://www.desktopmetal.com/products/shop

My Firefox Nightly version is: 135.0a1 (2024-11-26) (aarch64). My computer is a: MacBook Air (15-inch, M2, 2023) running macOS Sequoia (Version 15.1). I have been having these issues for a long time regardless of computer.

I have attached a picture of the labs settings I have enabled but I cannot see why any of them would affect this.