I did not know this and usually do not pay attention to ticket policies on ctrip or elong. Now, however, I got caught badly with a CZ Z fare booked on elong.

Ticketing conditions (including refund and modification) vary between travel agents! Unlike in e.g. Europe, the booking class does not define refund and modification conditions, but the travel agent does.

Example
Z-fare on CZ booked on:

CS-air.com: Refund 5%, Modification: free
Elong: No refund, no modification
Ctrip: Refund 50%, Modification: 20%

Y-fare on CZ booked on:

Cs-air.com: Free refund, free modification
Elong and Ctrip: Refund 5%, Modification: free

X-fare on MU booked on:

CEair.com: No refund, no modification
Ctrip: Refund: 80%, Modification: varies, ~penalty 200 RMB same booking class

Moral of the story, be careful to check the ticket policy at your travel agent. A W or Y will not always be free to cancel or change.