Non-Conformance Demo for WCAG 2.1 Success Criterion Success 1.4.4 Resize Text (Level AA)

1.4.4 Non-Conformance Shown with Non-Technical Explanation

The above heading overruns the page side when zoomed to 200% because the heading uses a fixed font size.

1.4.3 Non-Conformance CSS Markup and Technical Details

{font-size:128px;}

The font-size should be defined in relative rather than absolute terms. One way of doing that would be to use em (measured relative to the default font size, 2em would 2 times the font size) rather than px.