There are times when the oracle client on one's computer and the server version levels would not match (particularly when the DBA's are fast enough to get to the current level). One can see warning messages like this in TOAD.
So pl refer the metalink note 207303.1 (Client / Server / Interoperability Support Between Different Oracle Versions) which details the different versions that are supported at both client & server levels.
Note the version on the client can be same or newer than the server's.