position: temporal
'temporal' value would make a component disappear after a certain amount of seconds, like alerts or messages.
See other not-so-valid CSS things
collapsing: none
collapsing: none is an invalid CSS declaration I wish existed.
place: center
place: center is an invalid CSS declaration I wish existed.
font-family: system-font
font-family: system-font is an invalid CSS declaration I wish existed.
position-items: center
position-items: center is an invalid CSS declaration I wish existed.
position: temporal
position: temporal is an invalid CSS declaration I wish existed.
color: anthracite
color: anthracite is an invalid CSS declaration I wish existed.
float: top
float: top is an invalid CSS declaration I wish existed.