仅为 IE 添加样式表

add_action( 'wp_enqueue_scripts', 'enqueue_my_styles_and_scripts' );

/**
 * Enqueue styles (or scripts) conditionally.
 *
 * Load stylesheets (or scripts) specifically for IE. IE10 and above does
 * not support conditional comments in standards mode.
 *
 * @link https://gist.github.com/wpscholar/4947518
 * @link https://msdn.microsoft.com/en-us/library/ms537512(v=vs.85).aspx
 */
function enqueue_my_styles_and_scripts() {

    // Internet Explorer specific stylesheet.
    wp_enqueue_style( 'themename-ie', get_stylesheet_directory_uri() . '/css/ie.css', array( 'twentyfifteen-style' ), '20141010' );
    wp_style_add_data( 'themename-ie', 'conditional', 'lte IE 9' );

    // Internet Explorer 7 specific stylesheet.
    wp_enqueue_style( 'themename-ie7', get_stylesheet_directory_uri() . '/css/ie7.css', array( 'twentyfifteen-style' ), '20141010' );
    wp_style_add_data( 'themename-ie7', 'conditional', 'lt IE 8' );

}