Editing Module:Infobox/styles.css

/* {{pp|small=y}} */
/*
 * This TemplateStyles sheet deliberately does NOT include the full set of
 * infobox styles. We are still working to migrate all of the manual
 * infoboxes. See [[MediaWiki talk:Common.css/to do#Infobox]]
 * DO NOT ADD THEM HERE
 */
/*
 * not strictly certain these styles are necessary since the modules now
 * exclusively output infobox-subbox or infobox, not both
 * just replicating the module faithfully
 */
.infobox-subbox {
	padding: 0;
	border: none;
	margin: -3px;
	width: auto;
	min-width: 100%;
	font-size: 100%;
	clear: none;
	float: none;
	background-color: transparent;
}

.infobox-3cols-child {
	margin: auto;
}