Don't load lightbox.css on every page. Remove lightboxIE.css since we don't support IE6 and IE7 anymore.
Remove mentions of IE6 which is not supported any more.
Move the inline script after the external scripts to avoid blocking the parallel download.
Reduce the list of minification excludes.
XWIKI-8717: Upgrade to yuicompressor-maven-plugin version 1.3.2