mastodon-user-styles.css

/* indicate media without a description
initial code by Paul (https://linernotes.club/@balrogboogie), expanded upon by FiXato (https://contact.fixato.org)
related discussion: https://dragonscave.space/@Mayana/106443499687608116.
Feel free to reuse it; it's public domain (https://linernotes.club/@balrogboogie/106681622019395866) */
.media-gallery__item-thumbnail img:not([alt]),
.audio-player__canvas:not([title]),
.video-player video:not([title]), 
.media-gallery__gifv video:not([title])
{
    border: 2px solid red;
    box-sizing: border-box;
}

/* direct messages with different background color
   from https://weirder.earth/@not_on_pizza/107785229588405129 */
.status__wrapper-direct { background-color: #191f30 !important; }

/* make sure the menu button followed profiles doesn't vanish on thin columns */
.button.logo-button.button--destructive.button--with-bell {
    min-width: 0 !important;
}

/* increase min width per column; or fill full screen width if not enough columns */
.column, .drawer {
    flex: 1 1 auto;
    max-width: none;
    min-width: 25em;
}