After offering initial prayers to the deity in a temple, Hindus walk around the deity. This is to receive the positive vibrations that are present in the deity. In most temples the deity is installed in the temple in such a spot and using such metals that it emits magnetic waves. This positive vibrations influence the devotee.
Hindus move around the deity in clockwise direction. In this form, the devotee is moving along the magnetic field and thus benefits from positive vibrations are received.
One never completes the complete circle of walk in a Lord Shiva. The devotee starts to walk in clockwise direction and stops at the line where the offering of milk and water flows from the sanctum sanctorum. Thus only 3 quarter is completed. A devotee returns and completes the rest of the quarter in anticlockwise direction.
The popular belief is that in Shiva temples the vibrations are present in clockwise and anticlockwise.
You can read more on the same subject in this article – Importance of Pradakshina.