hb860

This plugin is a modification of the “Always valid lightbox” plugin created by <a href="http://www.joffrey-quillet.fr/" rel="nofollow ugc">Joffrey Quillet</a>. This mod contains a fix for the buggy image resizing and for the description text inside the lightbox popup. Also, it uses only the built-in jQuery library. <a href="http://winaero.com/blog/fix-markup-validation-issues-with-the-always-valid-lightbox-mod-plugin" rel="nofollow ugc">More info</a>.
Always Valid Lightbox is a Lightbox plugin whose markup adapts to the WP site’s Doctype, in order to always provide a valid HTML markup.
Also, AVL allows the user to chose the attributes he wants inserted on his image links, depending on the Doctype declaration used in the website header.php template. 
This way, the lightbox never generates markup validation errors at the W3C Validator test.
The jQuery lightbox effect is an adaptation based on David Ryan’s jQuery lightbox tutorial : http://dryan.com/articles/jquery-lightbox-tutorial/

Plugin Name: Always valid lightbox mod

Always Valid Lightbox Mod is a Lightbox plugin which adapts to site's DOCTYPE and provides a valid HTML markup.

ppalli

This plugin automatically add the rel=”lightbox[POST-ID]” to images linked in a post and in a comment, and recovers the image title. 
POST-ID is unique per post so all images per post are grouped in one LightBox set. 
Doesn’t add the files required for LightBox, it’s add the “rel lightbox” tag. 
You have to insert the required files yourself in your theme, you can use <a href="http://www.huddletogether.com/projects/lightbox2/" rel="nofollow ugc">Lightbox 2</a>, <a href="http://www.shadowbox-js.com/" rel="nofollow ugc">Shadowbox.js</a> or an other script, or use a plugin like <a href="https://wordpress.org/extend/plugins/shadowbox-js/" rel="ugc">Shadowbox JS</a>.

Add LightBox & Title

This plugin for WordPress automatically add the rel="lightbox[ID-OF-THE-POST]" and recovers the image title.

Plugin Name: Always valid lightbox mod vs Add LightBox & Title