您可以通过以下方式为该区域添加HTMLwp_footer, 包含样式wp_enqueue_style(), 并包含用于显示/隐藏弹出窗口的javascriptwp_enqueue_script().

wpse90382_popup_function() {
    add_action( \'wp_footer\', \'wpse90382_popup_html\' );
    wp_enqueue_style( \'your_style\', get_template_directory_uri() . \'your_stylesheet.css\' );
    wp_enqueue_script( \'your_script\', get_template_directory_uri() . \'your_javascript.js\' );
}
wpse90382_popup_html() {
    ?>
        <div>Your HTML</div>
    <?php
}
if ( some condition )
    wpse90382_popup_function();