The browser you are using is too old. OTRS runs with a huge lists of browsers, please upgrade to one of these. Please see the documentation or ask your admin for further information.
An upgrade for OTRS is scheduled for May 31st 2017, 14:00 UTC. The maintenance window will be 1 hour long, during which OTRS will be unavailable. The corresponding phabricator task is https://phabricator.wikimedia.org/T165284