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

1.4.4 Conformance Shown with Non-Technical Explanation

The above heading (as do most headings on this site) uses a relative font size that adjusts with page size.

1.4.4 Non-Conformance CSS Markup and Technical Details

{font-size:.85em;}

The font-size should be defined in relative rather than absolute terms. One way of doing that is to use em which is measured relative to the default font size. For example, .85em is 85% of the default font size.