Note from 23 November 2023
I wonder if MDN could add screenshots of the live examples, so people can see the result even if their browser doesn't support a feature yet.
For example for CSS Grid masonry layout:
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_grid_layout/Masonry_layout
I'm using Firefox, so I had to activate the layout.css.grid-template-masonry-value.enabled
flag to see the “good” result.