List Search Links

The mind must be given relaxation; it will arise better and keener after resting. As rich fields must not be forced-for their productiveness, the have no rest, will quickly exhaust them constantlabor will break the vigor of the mind, but if it is released and relaxed a little while, it will recover its powers
Seneca

:invalid

The :invalid CSS pseudo-class represents any <input> or other <form> element whose contents fail to validate.
:invalid css reference