MediaWiki:Common.css

/* CSS placed here will be applied to all skins */
.tinyimage {
  image-rendering: -moz-crisp-edges;
  image-rendering: pixelated;
  -ms-interpolation-mode: nearest-neighbor;
}
.tooltip{
  position: relative;
}

.tooltiptext {
  position: absolute;
  display: block;
  z-index: 2;
  width: 250px;
  padding: 10px;
  visibility: hidden;
  opacity: 0;
  white-space: normal;
  text-align: left;
  transition: all 0.2s;
  border: 1px solid #aaa;
  background-color: #ffdd66;
}

.tooltip:hover>.tooltiptext {
  visibility: visible;
  opacity: 1;
}