Hi, One of the WCAG requirements is to have all our CSS Level 2.1 valid. I saw we have exceptions on the elements we cover in our validation and I would like to know your opinion about: *opacity* CSS propriety. *Opacity* is a CSS 3 valid property, but not a CSS 2.1. The main components (that I know) that can be affected by not having * opacity* are: modalPopup.css (for Ctrl+G "Go To" feature) and lightbox.css (for the boxes in Administation: Users, Groups). Without *opacity* they look disconnected from XWiki. *Opacity* used to be used in Panel Wizard, but got removed because of the WCAG and because it didn't changed much on an aspect level. It can be used in lots of places like tooltips, use to be in WYSIWYG disabled buttons etc. The main problem about *opacity* is that if we are gonna make it an exception, because of IE6, we are gonna need to make other proprieties exceptions (*filter, zoom*). IE’s CSS uses *filter* instead of *opacity* and also needs (for some elements) *zoom* propriety in order to apply it correctly. I need to know your opinion in order to complete our CSS files validation.