I'm working on a page (

CodePudding user response：

It could be because you are using em instead of rem.

em is the size of the font that applies to the parent of the element. rem is applied to root of the element.

CodePudding user response：

Solution: The difference in font-weight was caused by styling that was making the header text lighter, and NOT (as I had assumed) styling that was making the text lower in the page heavier.

I had checked all of the article and section CSS for font weight, but had failed to check the header styling.

Thank you to everybody who commented!