CSS to make un-described images more evident

mastodon-pics-no-description.css

/* 
 * Use this CSS either as a browser stylesheet or, if you run your own instance, as Site Custom CSS, to 
 * make images without alt-text obvious in your web interface.
 *
 * Hover over any obscured image to view it normally.
 *
 * Safari user stylesheet: Safari -> Settings -> Advanced Stylesheet
 * Chrome / Firefox: see https://www.thoughtco.com/user-style-sheet-3469931
 * Mastodon (v4) admin: Preferences -> Administration -> Appearance -> Custom CSS
 */
.app-holder#mastodon img:not([alt]) {
  border: solid red 12px !important;
  opacity: 0.2;
  width: 95%;
  height: 90%;
}
.app-holder#mastodon img:not([alt]):hover {
  border: none !important;
  opacity: 1;
  width: 100%;
  height: 100%;
}