"how to setup voice and data ports on the catalyst switch ?"
Usually like this example: (BTW, you determine the VLANs you wish to use for data and voice.)
Switch(config)#interface GigabitEthernet 0/1
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 100
Switch(config-if)#switchport voice vlan 101
Switch(config-if)#exit
Switch(config)
"is there a difference between people using IP phone and others using web-client ?"
Maybe, maybe not. Often IP phones are set to work with tagged frames, as in the above example config. Web-clients might only support using the data (untagged) VLAN on the access port.