Respond.js on CDN
<?php
function woo_load_responsive_IE_footer () {
$html = '';
echo '<!--[if lt IE 9]>'. "\n";
echo '<script src="' . get_stylesheet_directory_uri() . '/includes/respond/src/respond.js"></script>'. "\n";
echo '<link href="' . get_stylesheet_directory_uri() . '/includes/respond/cross-domain/respond-proxy.html" id="respond-proxy" rel="respond-proxy" />'. "\n";
echo '<link href="' . get_stylesheet_directory_uri() . '/includes/respond/cross-domain/respond.proxy.gif" id="respond-redirect" rel="respond-redirect" />'. "\n";
echo '<script src="' . get_stylesheet_directory_uri() . '/includes/respond/cross-domain/respond.proxy.js"></script>'. "\n";
echo '<![endif]-->'. "\n";
echo $html;
} add_action( 'wp_footer', 'woo_load_responsive_IE_footer', 10 );
?>