Always Valid Lightbox Mod is a Lightbox plugin which adapts to site's DOCTYPE and provides a valid HTML markup.
This plugin is a modification of the "Always valid lightbox" plugin created by Joffrey Quillet. 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. More info.
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/