I did use Theme Check for a review of the site and that was what i found (the most of the warmings must be like that, but some of them could be fix maybe).
REQUIRED: This theme doesn't seem to display tags. Modify it to display tags in appropriate locations.
REQUIRED: Text Domain: is missing from your style.css header.
REQUIRED: License: is missing from your style.css header.
REQUIRED: License URI: is missing from your style.css header.
REQUIRED: .gallery-caption css class is needed in your theme css.
REQUIRED: .bypostauthor css class is needed in your theme css.
RECOMMENDED: This theme contains no sidebars/widget areas. See Widgets API
Warning: More than one text-domain is being used in this theme. This means the theme will not be compatible with WordPress.org language packs.
The domains found are pressbooks, /wp-login.php class=login>login here
You can also set up your own Pressbooks book at: Pressbooks.com.
WARNING: Your theme appears to be in the wrong directory for the theme name. The directory name must match the slug of the theme. This theme's correct slug and text-domain is luther.
(If this is a child theme, you can ignore this error.)
WARNING: Found a translation function that is missing a text-domain. Function _e, with the arguments 'pressbooks'
WARNING: Found a translation function that has an incorrect number of arguments. Function _e, with the arguments 'This book is private, and accessible only to registered users. If you have an account you can WARNING: Found PHP short tags in file page-cover-top-block.php.
Line 32: <p class='book-author'><?= $metadata['pb_contributing_authors']; ?> </p>
Line 100: <a rel='nofollow' onclick='<?= $tracking; ?>' itemprop='offers' itemscope itemtype='http://schema.org/
Line 101: <span class='export-file-icon small <?= $filetype; ?>' title='<?= esc_attr( $filename ); ?>'></span>
WARNING: .gitignore Hidden Files or Folders found.
REQUIRED: You are not allowed to hide the admin bar.
REQUIRED: The theme must not used the <title> tags.
REQUIRED: The theme must not call to wp_title().
REQUIRED: The <title> tags can only contain a call to wp_title(). Use the wp_title filter to modify the output
REQUIRED: Please remove any extraneous directories like .git or .svn from the ZIP file before uploading it.
REQUIRED: No reference to add_theme_support( "title-tag" ) was found in the theme.
REQUIRED: No content width has been defined. Example:
if ( ! isset( $content_width ) ) $content_width = 900;
REQUIRED: Could not find the comment-reply script enqueued. See: Migrating Plugins and Themes to 2.7/Enhanced Comment Display
<?php if ( is_singular() ) wp_enqueue_script( "comment-reply" ); ?>
REQUIRED: Could not find add_theme_support( 'automatic-feed-links' ). See: add_theme_support
<?php add_theme_support( $feature ); ?>
REQUIRED: get_option('home') was found in the file sidebar.php. Use home_url() instead.
Line 10: <li class='admin-btn'><a href='<?php echo get_option('home'); ?>/wp-admin'><?php _e('Admin', 'pressbooks'); ?></a></l
Line 13: <li class='home-btn'><a href='<?php echo get_option('home'); ?>'><?php _e('Home', 'pressbooks'); ?></a></li>
Line 16: <li class='toc-btn'><a href='<?php echo get_option('home'); ?>/table-of-contents'><?php _e('Table of Contents', 'pr
REQUIRED: get_option('home') was found in the file page-cover-top-block.php. Use home_url() instead.
Line 12: <a href='<?php echo get_option('home'); ?>/wp-admin'><?php _e('Admin', 'pressbooks'); ?></a>
Line 62: <a class='btn black' href='<?php echo get_option('home'); ?>/buy'><span class='buy-icon'></span><?php _e('Buy', '
REQUIRED: get_option('home') was found in the file header.php. Use home_url() instead.
Line 83: <a href='<?php echo get_option('home'); ?>/buy' class='button-red'><?php _e('Buy', 'pressbooks'
REQUIRED: get_bloginfo('url') was found in the file functions.php. Use home_url() instead.
Line 183: $bloginfourl= get_bloginfo('url'); ?>
REQUIRED: get_bloginfo( 'url' ) was found in the file page-buy.php. Use home_url() instead.
Line 19: <p><?php printf( __( 'You can buy <a href='%1$s'>%2$s</a> by following any of the links below:', 'pressbooks' ), get_bloginfo( 'url' ), get_bloginfo( 'name' ) ); ?></p>
REQUIRED: bloginfo('url') was found in the file functions.php. Use echo esc_url( home_url() ) instead.
Line 183: $bloginfourl= get_bloginfo('url'); ?>
REQUIRED: bloginfo('template_url') was found in the file page-cover-private-block.php. Use echo esc_url( get_template_directory_uri() ) instead.
Line 2: <a href='http://pressbooks.com' class='pressbooks-brand'><img src='<?php bloginfo('template_url'); ?>/images/pressbooks-branding-2x.png' alt='pressb
REQUIRED: bloginfo('template_url') was found in the file functions.php. Use echo esc_url( get_template_directory_uri() ) instead.
Line 682: <a href='https://pressbooks.com' class='pressbooks-brand'><img src='<?php bloginfo('template_url'); ?>/images/pressbooks-branding-2x.png' alt='pressb
REQUIRED: bloginfo('template_directory') was found in the file page-buy.php. Use echo esc_url( get_template_directory_uri() ) instead.
Line 23: <li class='buy-amazon'><a href='<?php print $urls['amazon']; ?>' class='bookstore-logo-link logo'><img src='<?php bloginfo('template_directory'); ?>/images/amazon.png' width='100' height='2
Line 27: <li class='buy-oreilly'><a href='<?php print $urls['oreilly']; ?>' class='bookstore-logo-link logo'><img src='<?php bloginfo('template_directory'); ?>/images/oreilly.png' width='100' height='
Line 31: <li class='buy-barnes-and-noble'><a href='<?php print $urls['barnesandnoble']; ?>' class='bookstore-logo-link logo'><img src='<?php bloginfo('template_directory'); ?>/images/barnes-and-noble.png' width='100'
Line 35: <li class='buy-kobo'><a href='<?php print $urls['kobo']; ?>' class='bookstore-logo-link logo'><img src='<?php bloginfo('template_directory'); ?>/images/kobo.png' width='54' height='29'
Line 39: <li class='buy-ibooks'><a href='<?php print $urls['ibooks']; ?>' class='bookstore-logo-link logo'><img src='<?php bloginfo('template_directory'); ?>/images/ibooks.png' width='34' height='34
REQUIRED: bloginfo('stylesheet_directory') was found in the file header.php. Use echo esc_url( get_stylesheet_directory_uri() ) instead.
Line 17: <link rel='shortcut icon' href='<?php bloginfo('stylesheet_directory'); ?>/favicon.ico' />
REQUIRED: bloginfo( 'url' ) was found in the file page-buy.php. Use echo esc_url( home_url() ) instead.
Line 19: <p><?php printf( __( 'You can buy <a href='%1$s'>%2$s</a> by following any of the links below:', 'pressbooks' ), get_bloginfo( 'url' ), get_bloginfo( 'name' ) ); ?></p>
RECOMMENDED: Possible variable $metakeys found in translation function in footer.php. Translation function calls must NOT contain PHP variables.
Line 32: <td><?php _e($metakeys[$key], 'pressbooks'); ?>:</td>
RECOMMENDED: Possible variable $bloginfourl found in translation function in functions.php. Translation function calls must NOT contain PHP variables.
Line 188: <div class='entry_content denied-text'><?php _e('This book is private, and accessible only to registered users. If you h
RECOMMENDED: No reference to post-thumbnails was found in the theme. If the theme has a thumbnail like functionality, it should be implemented with add_theme_support( "post-thumbnails" )in the functions.php file.
RECOMMENDED: No reference to nav_menu's was found in the theme. Note that if your theme has a menu bar, it is required to use the WordPress nav_menu functionality for it.
RECOMMENDED: No reference to the_post_thumbnail() was found in the theme. It is recommended that the theme implement this functionality instead of using custom fields for thumbnails.
RECOMMENDED: No reference to add_theme_support( "custom-header", $args ) was found in the theme. It is recommended that the theme implement this functionality if using an image for the header.
RECOMMENDED: No reference to add_theme_support( "custom-background", $args ) was found in the theme. If the theme uses background images or solid colors for the background, then it is recommended that the theme implement this functionality.
RECOMMENDED: No reference to add_editor_style() was found in the theme. It is recommended that the theme implement editor styling, so as to make the editor content match the resulting post output in the theme, for a better user experience.
RECOMMENDED: Could not find the file readme.txt in the theme. Please see Theme_Documentation for more information.
RECOMMENDED: Tags: is either empty or missing in style.css header.
INFO: Possible hard-coded links were found in the file page-cover-private-block.php.
Line 2: <a href='http://pressbooks.com' class='pressbooks-brand'><img src='<?php bloginfo('t
INFO: Possible hard-coded links were found in the file functions.php.
Line 188: <div class='entry_content denied-text'><?php _e('This book is private, and accessible only to registered users. If you have an account you can <a href=''. $bloginfourl .'/wp-login.php' class='login'>login here</a> <p class='sign-up'>You can also set up your own Pressbooks book at: <a href='http://pressbooks.com'>Pressbooks.com</a>.', 'pressbooks'); ?></p></div>
Line 682: <a href='https://pressbooks.com' class='pressbooks-brand'><img src='<?php bloginfo('
INFO: Possible hard-coded links were found in the file footer.php.
Line 51: <p class='cie-name'><a href='http://pressbooks.com'><?php _e('Pressbooks.com: Simple Book Production', '
INFO: Possible hard-coded links were found in the file content-social-footer.php.
Line 7: <li class='twitter'><a href='https://twitter.com/share' class='twitter-share-button' data-count='horizon
INFO: Non-printable characters were found in the functions.php file. You may want to check this file for errors.
Line 188: <div class='entry_content denied-text'><?php _e('This book is private, and accessible only to registered users. If you have an account you can <a href=''. $bloginfourl .'/wp-login.php' class='login'>login here</a> ��<p class='sign-up'>You can also set up your own Pressbooks book at: <a hr