a:unknown { }
a:Unknown { }
a:uNkNoWn { }
a:UNKNOWN { }
a:pseudo-class { }
body:not(div):noot(span) {}
a:unknown::before { }
a,
b > .foo:error { }
::-webkit-scrollbar-button:horizontal:unknown {}
:first { }
:slotted {}
:placeholder {}
@page :blank:unknown { }
@page foo:unknown { }
:horizontal:decrement {}
