Since 11 version Internet Explorer asks for its configuration file, which does not exist in Zabbix frontend:

[Wed Sep 09 08:13:31 2015] [error] [client 192.168.3.1] File does not exist: /usr/share/zabbix/browserconfig.xml

It could be ignored by adding "<meta name="msapplication-config" content="none"/>" header option.

More information: https://msdn.microsoft.com/en-us/library/dn320426(v=vs.85).aspx