May I suggest that a) the "permission denied" error message is improved to say what exactly the problem is (it doesn't even tell you you're linking to a "forbidden" site, much less which one), that b) Wikipedia is added to the whitelist (shortcuts nonwithstanding, I see no issue with linking to Wikipedia using regular a tags), and c) that the bullet points below the "comment on" form, when listing approved HTML tags, caution that a is restricted in its use?