As this is a question from my client im here to clarify.
Is it possible to user Oracle 10G client to access a Oracle 11G Database?
If so will it create any problem in future?
Please DBA's give me your suggestion thanks in advance.
Classifiy 10g and 11g, these are marketing labels, no software versions like 10.2.0.1 and 184.108.40.206. Assuming you mean 10gR2 (10.2.0.x) and 11gR2 (11.2.0.x), there's technically no problem.
There's a support problem, 10gr2 is now out of Premier Support and in Extended Support. If you don't have an Extended Support contract, no support , no patches.
That could be bad for production environments.