Netsurf
An independent, lightweight web browser.
Netsurf is an actively developed, independent browser with good support for CSS 2.1—the era before flexbox and grid—along with some genuinely useful newer features, @media queries among them.
Notes on Supporting Netsurf
Netsurf does not support display: flex, and that needn’t be a problem. Float-based layouts—and table-based layouts, if it comes to that—work in ordinary browsers and in Netsurf both. Look at a web design from the early 2000s and see what kinds of layout are possible.
Netsurf ignores CSS inside a @supports block. If a layout can’t be done with floats alone, start with a base layout that Netsurf can render and then progressively enhance it for browsers that support the newer features.
Use @media queries with px values to adjust for smaller screens. Often that means dropping a float when the screen is too narrow, so items stack instead of sitting side by side.
Netsurf only supports generic font families and will not display a custom font, even one installed on the machine running it. Which is a good exercise: learning to lean on design fundamentals like contrast and spacing is a sound place to start a design anyway, rather than on whatever is currently fashionable in typography. The families it supports:
sans-serifserifmonospacecursivefantasydefault