I'm really liking parenscript and just got started with it, so this question might be off base, but here goes... I'm writing a parenscript/cl-who/hunchentoot application, and I'm using some code along the lines of: (css-to-string '(((a.foo) (:color "green" :font-size "25pt")) ((a.foo\:hover) (:color "red")))) which generates the following string: "A.FOO { color:green; font-size:25pt; } ; A.FOO:HOVER { color:red; } " Firefox doesn't seem to like the second rule, since it starts with a semicolon. The code of css-to-string I have is: (defun css-to-string (rules) (string-join (mapcar #'css-rule-to-string rules) "; ")) If I substitute it with (defun css-to-string (rules) (concatenate 'string (mapcar #'css-rule-to-string rules))) That problem goes away and Firefox recognizes the second rule. Am I doing something wrong or is this a bug?