What is a good innovation? Is it wrong if we act according to it sometimes?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

A good innovation, as the scholars of the principles of Islamic jurisprudence define it, is anything that has evidence in religion. The statements of some scholars from our Salaf who mentioned that some innovations are good, referred to the linguistic meaning of the word innovation (Bid'ah) and not in religion. Like the statement of 'Umar about Taraaweeh prayers: "What a good innovation that is!" So, it is only in this regard that we may say a good innovation. 

Allaah Knows best.