I have a templating css file type that allows comments to start with '##' No matter what I try though It doesn't seem to recognize this in my derived-mode. Here is what i have so far
(define-derived-mode cheetah-css-mode css-mode "cheetah-css"
(make-face 'cheetah-css-variable-face)
(font-lock-add-keywords
nil
'(("\\(##.*\\)\n" font-lock-comment-face)) (font-lock-mode 1)))