The first two lines:
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
/etc/protocols these two correspond to IPSec:
esp 50 IPSEC-ESP # Encap Security Payload [RFC2406]
ah 51 IPSEC-AH # Authentication Header [RFC2402]
The third line:
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 188.8.131.52 -j ACCEPT
/etc/services udp port 5353 is multicast DNS:
mdns 5353/udp # Multicast DNS
And last, but not least:
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
These ones correspond to cups printing services.
ipp 631/tcp # Internet Printing Protocol
Related to your 'do I need them?' question, it depends:
- Is it a vpn server?
- Do you use multicast dns? Seems to be used by services like Apple's bonjour
- Is it a printing server?
Since you state that it is a "web server with ftp, apache, ssh, mysql" I don't think you need them.
Besides, another question is: why are these rules? You probably have packages you don't need on the server.