。
Don't you dare leave the toilet lid open.
Literal
Absolutely toilet [possessive-の] lid [object-を] opened-state [at-に] do-[prohibition-な][emphatic-よ].
絶対 'absolutely' intensifies the prohibition. 蓋を開けたままにする 'to leave the lid open' — ~たまま marks a persisting state. するなよ is the plain prohibition + emphatic よ. A common household battle — the eternal toilet-lid argument.