I want to use
in chrome, but
in firefox. if I declare only the overlay value, then firefox would not scroll at all. I know that overlay is not standard but this shall be perfectly irrelevant for now.
my question is, which is the best way to have each browser the value as described.
is it possible to have a fallback inside CSS alone? cannot think that there is, but maybe there is a trick.
You just supply both of them, the browser will use the last recognized one.
Or you might want consider apply different styles for different browsers https://www.browserstack.com/guide/create-browser-specific-css