i can not restor my ipad2 by using itunes. always got error number 9.so what should i do?

The iPad in my experience is very picky about what cables it will restore with. Error 9 is almost always related to the cable, NOT the dock connector/flex cable. Use the official Apple cable if you still have it, or borrow one from a friend.

If that doesn't work, it might also have something to do with the IPSW you are trying to restore with. Try using a different IPSW or using to boot dfu mode and restore like that. It could be this because error 9 can be related to the ramdisk kernel rejecting the ASR because it is not signed properly, thus breaking the connection with the device and causing error 9.

i Dunno if apple has any ispw except the newest updates... Download one online if so