Cannot get font-size smaller than 14px
Briefly

It’s possible that a browser default setting or the CSS for the website could enforce minimum font sizing, preventing smaller sizes from applying properly.
Check for styles applied to your stylesheet that might be overriding your changes. Developer tools in the browser can be handy for identifying any conflicts.
Another factor could be your CSS Reset stylesheet, which may enforce a minimum font size for certain elements. Review any reset or normalize CSS for potential overrides.
If the font-family is applied through a parent container with a larger font size, it could restrict child elements, leading to inconsistencies in applying smaller sizes.
Read at SitePoint Forums | Web Development & Design Community
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