> Specifically, I'd like to create a plugin to echo the following in the > header immediately after the default stylesheet The preferred way is to *enqueue* it, with the default/main stylesheet as the *dependency*. Here's a demo plugin, with the structure: + plugins/ | +--+ my-ie-style/ | +--+ my-ie-style.php | +--+ css/ | +--+ ie.css where the `my-ie-style.php` file is: <?php /** * Plugin Name: Demo - My IE style * Plugin URI: http://wordpress.stackexchange.com/a/85496/26350 * Description: Enqueue With IE conditional, depending on the main-style stylesheet * Author: wpse * Version: 1.0.0 */ add_action( 'wp_enqueue_scripts', function() { // Register wp_register_style( 'my-ie-style', // handle plugin_dir_url( __FILE__ ) . 'css/ie.css', // file [ 'main-style' ], // dependency <-- ADJUST THIS! '1.0.0', // version 'all' // media ); // Enqueue wp_enqueue_style( 'my-ie-style' ); // Add IE conditional wp_style_add_data( 'my-ie-style', // handle 'conditional', // key ('conditional', 'rtl', 'suffix', 'after', 'alt', 'title') 'IE' // value ); } ); This will generate the following within the `<head>` tag: <link rel='stylesheet' id='main-style-css' href='http://example.tld/wp-content/themes/mytheme/style.css?ver=4.5.3' type='text/css' media='all' /> <!--[if IE]> <link rel='stylesheet' id='my-ie-style-css' href='http://example.tld/wp-content/plugins/my-ie-style/css/ie.css?ver=1.0.0' type='text/css' media='all' /> <![endif]--> where our *custom* IE stylesheet loads after the *main* stylesheet. Hopefully you can adjust it to your needs.