There's at least one player out there with a skill which is over 20, it's 21 in fact. The style of the link to the skill is a.lev21. I'm assuming that doesn't exist, since the skill name ("legendary", still) displays in a non-bold, non-coloured font. The title text is "21".
(I'm not listing the player since he's on the transfer list, and you shouldn't either. I can provide the ID to anyone that needs it.)
I don't have an example, but I've seen similar styling issues with a sub-atrocious (0) skill.