  It is shown that the differential form of Friedmann equations of FRW universe
can be recast as a similar form of the first law, $T_{h}dS_{h} = dE + WdV$, of
thermodynamics at the apparent horizon of FRW universe filled with the viscous
fluid. It is also shown that the generalized second law of thermodynamics holds
at the apparent horizon of FRW universe and preserves dominant energy
condition.
