Ask IE not to use compatibility view (Note: may not work with caching plugins; use Apache/nginx to send headers instead)

functions.php

<?php 
// Don't copy the opening <?php tag above!

// Send headers to ask IE NOT to use compatibility mode
add_filter( 'wp_headers', 'genesis_keep_ie_modern' ); 
function genesis_keep_ie_modern( $headers ) {
	if ( isset($_SERVER['HTTP_USER_AGENT']) && (strpos( $_SERVER['HTTP_USER_AGENT'], 'MSIE' ) !== false) ) {
		$headers['X-UA-Compatible'] = 'IE=edge';
	}
	return $headers;
}