Matt Martz

achmafooma

Moves the gallery shortcode styles to the head so it doesn’t break XHTML 
validation; allows disabling or modifying the default gallery styles.
By default when using the WordPress gallery, the styles are placed into the 
post content which breaks XHTML validation. This plugin moves the style into 
the head of the page using a look-ahead to determine if the [gallery] 
shortcode is used in any posts.
This plugin also gives you the option to modify the default gallery style 
CSS or disable the gallery styles entirely (so you can control it from your 
template CSS files).
This plugin uses ideas recommended in a patch located at 
https://trac.wordpress.org/attachment/ticket/6380/6380-style.diff
Special thanks to 
* The original author: Matt Martz, http://sivel.net 
* Serbo-Croatian (sr_RS) translation: Borisa Djuraskovic, http://www.webhostinghub.com 
* Spanish (es_ES) translation: Ogi Djuraskovic, http://www.webhostinghub.com/

Gallery Shortcode Style to Head

Moves the gallery shortcode styles to the head so it doesn't break XHTML validation; allows disabling or modifying the default gallery styles.

Weston Ruter

This plugin is developed at <a href="http://www.shepherd-interactive.com/" title="Shepherd Interactive specializes in web design and development in Portland, Oregon" rel="nofollow ugc">Shepherd Interactive</a> 
for the benefit of the community. No support is available. Please post any questions to the <a href="https://wordpress.org/tags/xhtml5-support?forum_id=10" rel="ugc">support forum</a>.
Allows templates to serve XHTML5 markup by adding the necessary JavaScript shim for IE7+, and for IE6 by converting all new elements to <code>div</code>s and <code>span</code>s with class names that contain the original HTML5 element name prefixed by “<code>html5-</code>“, for example: <code><article></code> becomes <code><div class="html5-article"></code> 
and <code><time></code> becomes <code></code>
If the browser supports XHTML, the content is served with the <code>application/xhtml+xml</code> 
MIME type. This can be disabled by placing <code>remove_filter('option_html_type', 'xhtml5support_filter_html_type')</code> 
in <code>functions.php</code>.
Note that print stylesheets do not get applied to IE7+ even with the shim, so if you are relying on the ability for IE users to print properly-styled pages, you must force the IE6 renaming behavior for all versions of IE by doing <code>update_option('xhtml_support_add_msie_shims', false);</code>

XHTML5 Support

Allows templates to serve XHTML5 markup by adding the necessary JavaScript shim for IE7+ and by converting all new elements to divs and spans with app …

Gallery Shortcode Style to Head vs XHTML5 Support