.myEl,
.myEl:focus-within {
/* ... */
}
The `:focus-within` pseudo-class doesn't work on IE, as the CanIUse chart shows, thus the above CSS rule gets invalidated entirely according to specs.
"TL;DR"
Fancy new CSS selectors within groups of selectors can break your stuff.
ALT caniuse.com chart on :focus-within support
ALT w3.org specs on groups of selectors