Designed for Firefox
I would recommend removing the "Designed for Firefox" text on the bottom of the site. It's certainly not a good practice to design websites for a specific web browser, and designing specifically for Firefox is as evil as designing for IE.
It would be much better to make the website w3c compliant and then put the "Valid XHTML" mark instead.
Unfortunately, it's not the case since there is something about 100 validation errors on the main page: http://validator.w3.org/check?uri=http%3A%2F%2Fwww.nuxified.org%2F
Thus, I would just suggest removing the text for now.