I have just seen the block diagram of the amplifier TDA7266L from the thread:http://forum.allaboutcircuits.com/showthread.php?t=85846
I am curious to know about the usefulness of capacitors C5, C6 in the diagram.

 

They are power filter capacitances to minimize noise on the power and avoid instability in the circuit caused by high power connection impedance. The are used in all properly designed circuits.

The small 100nF capacitor should be connected directly from the power to the ground as close to the IC as feasible.

Read this.