This will help you to block your HTTP data specially the Facebook what is most common for the corporate world. All the system administrator want to block it let me show you how to block it by step by step

Log in to mikrotik

go to IP Firewall > Filter Rules > General

Select >Chain = Forward

Src-Add= (Your LAN's Network Address with Subnet Mask)

Select> Advance Tab

go to> Content > add> facebook.com.*

Select> Action Tab

go to> Action > Reject with icmp admin prohibited

or // select action>drop and apply > ok

select facebook firewall rule >click >enable

and you will get the result .