Template:Tooltip/styles.css

.tooltip {
	position: relative;
	display: inline-block;
	border-bottom: 1px dotted black;
}

.tooltip .tooltiptext {
	visibility: hidden;
	position: absolute;
	z-index: 1;
	min-width: 120px;
	padding: 5px 0;
	border-radius: 6px;
	background-color: #aaa;
	color: #000;
	text-align: center;
}

.tooltip:hover .tooltiptext {
	visibility: visible;
}