Images of Text (No Exception)
Images of text are only used for pure decoration or where a particular presentation of text is essential to the information being conveyed, such as a logotype.
In plain language
This is the strictest version of the "no images of text" rule: text should almost never be an image — only when it's purely decorative or a real exception like a logo.
Why it matters
An image of text can't be resized cleanly, can't have its color or font changed to suit someone's needs, and doesn't adapt at all — unlike real text, which every user can customize to what they can actually read.
In practice
Fails this criterion
A page shows its navigation menu labels as text baked into image files, so users can't resize or recolor them for readability.
Meets this criterion
The same navigation labels are real HTML text styled with CSS, so anyone can resize, recolor, or otherwise adjust them — with the only image of text being the site's logo.
Test it yourself
Try to select and zoom into any text-like content on the page. If it's actually an image (can't be selected, gets blurry when zoomed) and it's not a logo or another essential exception, this criterion is failing.