Source

File: wp-includes/formatting.php

function print_emoji_styles() {
	static $printed = false;

	if ( $printed ) {
		return;
	}

	$printed = true;

	$type_attr = current_theme_supports( 'html5', 'style' ) ? '' : ' type="text/css"';
	?>
<style<?php echo $type_attr; ?>>
img.wp-smiley,
img.emoji {
	display: inline !important;
	border: none !important;
	box-shadow: none !important;
	height: 1em !important;
	width: 1em !important;
	margin: 0 .07em !important;
	vertical-align: -0.1em !important;
	background: none !important;
	padding: 0 !important;
}
</style>
	<?php
}