Is it obligatory to invoke blessings upon the Prophet (peace be upon him and his family) 40 times when browsing fatwas?

Praying upon the Prophet, peace and blessings be upon him, is a good deed and a great act of closeness to Allah. Allah will bless you if you pray upon His Prophet. It is not obligatory to pray upon him every time his name is mentioned; rather, it is a Sunnah. Therefore, there is no sin in omitting it, but your prayer upon him is better for you and carries a greater reward.