Note: The :blank selector is considered at risk, as the CSSWG keeps changing it.
See CSSWG issue #1967.
The :blank CSS pseudo-class selects empty user input elements (e.g. <input> or <textarea>).
Syntax
:blank {
/* ... */
}
Examples
Simple :blank example
In eventual supporting browsers, the :blank pseudo-class will enable developers to highlight in some way input controls that are not required, but still have no content filled in, perhaps as a reminder to users.
HTML
<textarea></textarea>
CSS
textarea:blank {
border: 3px solid red;
}