error on UI

I would like to give some feedback about ...

on this page http://www.checkio.org/mission/brackets/publications/add/

some symbols are displayed as

 i<len(expression)

and some are not displayed at all (such as curly brackets)

Thank You.

From: http://www.checkio.org/mission/brackets/publications/add/

HTTP_USER_AGENT:

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/37.0.2062.120 Safari/537.36