In OpenVZ type server virtualization, this message can happen:

Warning: Unknown iptable module: xt_connlimit, skipped
It can mean that in OpenVZ is telling You that a VPS should get iptable module, but this module is not available on the root/host server. So possible things you can do is do commands on the host server:

modprobe module_name
(example: modprobe xt_connlimit)

to install module.

Then you can try accessing virtual machine (VPS) again and repeating if the error will appear. If error appear, you can try editing virtual machine (VPS) config file ie command: vi /etc/vz/conf/yourvmid.conf and removing the module name from the last line in that file.

Another error that can happen:
FATAL Error: iptables: Unknown error 18446744073709551615