Zabbix frontend checks pre-requisites during the configuration (e.g. "memory_limit", "max_input_time", etc). It would be great to check "arg_separator.output" parameter also. Otherwise, an incorrect value may cause issue with the frontend. Examples (e.g. "arg_separator.output" has "&amp" value):

• instead of "CONFIGURATION OF ITEMS" Frontend will open "PERSONAL DASHBOARD"
• instead of simple graph, it will display "Zabbix has received an incorrect request. Field "itemids" is mandatory" error.