Question: There are some mistakes which occur whilst making tawaaf, what are those mistakes?

Response:
Many pilgrims adhere to specific supplications whilst making tawaaf. There are groups from amongst them that take (their supplications) from one designated to read and then they all repeat this as a group in chorus. This is a mistake from two points:

Firstly: This is adhering to a supplication which is not mentioned to be adhered to in the this place (tawaaf) because no specific supplication has been mentioned on the authority of the Prophet (sal-Allaahu `alayhe wa sallam) whilst making tawaaf;

Secondly: The group supplication in chorus is an innovation, which also interferes with the (concentration of) other pilgrims making tawaaf. That which is legislated is for everyone to supplicate on their own without raising the voices.

Shaykh Ibn Fowzaan
al-Bid'u wal-Muhdathaat wa maa laa Asla lahu - Page 398;
al-Fataawa Fadheelatush-Shaykh Saalih Ibn Fowzaan al-Fowzaan - Volume 2, Page 30

Taken from fatwa-online.com