mains       = rocket_get_dns_prefetch_domains();

		if ( (bool) $domains ) {
			foreach ( $domains as $domain ) {
				$dns_link_tags .= '<link rel="dns-prefetch" href="' . esc_url( $domain ) . '" />';
			}
		}

		$old_ie_conditional_tag = '';

		/**
		 * Allow to print an empty IE conditional tag to speed up old IE versions to load CSS & JS files
		 *
		 * @since 2.6.5
		 *
		 * @param bool true will print the IE conditional tag
		 */
		if ( apply_filters( 'do_rocket_old_ie_prefetch_conditional_tag', true ) ) {
			$old_ie_conditional_tag = '<!--[if IE]><![endif]-->';
		}

		// Insert all DNS prefecth tags in head.
		$buffer = preg_replace( '/<head(.*)>/', '<head$1>' . $old_ie_conditional_tag . $dns_link_tags, $buffer, 1 );

		return $buffer;
	}
}