Editing Template:Infobox/styles.css

/**
 * Common TemplateStyles used by [[Template:Extension]], [[Template:Skin]],
 * [[Template:Tool]], etc.
 */
.infobox {
	box-sizing: border-box;
	border: 2px solid #a2a9b1;
	width: 280px;
	border-collapse: collapse;
	border-spacing: 0;
	background-color: white;
	/* these are overriden by .infobox-rtl on the templates of interest */
	/* @noflip */
	clear: right;
	/* @noflip */
	float: right;
	/* @noflip */
	margin: 0 0 0.5em 0.5em;
}

.infobox th {
	/* @noflip */
	text-align: center;
}

@media (max-width: 719px) {
	/* high specificity to ensure specific infoboxes won't override these
	 * properties with their own tstyles inadvertently */
	body.mediawiki .infobox {
		float: none;
		clear: both;
		width: 100%;
		margin: 0 0 .5em 0;
	}
}

.infobox td {
	padding: 0.2em 0.5em;
}

.infobox tr {
        border: 1px solid #a2a9b1;
}

.infobox p {
        margin: 0.5em 0;
}

.infobox-header {
	background-color: #f8f9fa;
	text-align: left;
}

.infobox-header a {
	color: #FFF;
}

.infobox-header td,
.infobox-header th {
	padding: 0.5em 0;
}

.infobox-header img {
	padding: 0 0 0 0.5em;
}