What is the ruling on one who performs Hajj to the Sacred House of Allah and then reverts to watching bad websites?

The signs of a sound repentance are that the servant is better after it than before it. If the servant repents after committing a sin, then he is on the right path. However, one must beware of persisting in disobedience so that its abhorrence does not fade from the heart, and so that the servant is not prevented from repentance, in fulfillment of the Almighty's saying: "O you who have believed, respond to Allah and to the Messenger when he calls you to that which gives you life. And know that Allah intervenes between a man and his heart and that to Him you will be gathered." (Al-Anfal: 24).

The servant's repentance is encompassed by two acts of repentance from Allah: a preceding one (permission and facilitation) and a subsequent one (acceptance and reward). One must continue to strive against the self and not despair, in fulfillment of the Almighty's saying: "And those who strive for Us – We will surely guide them to Our ways. And indeed, Allah is with the doers of good." (Al-Ankabut: 69).

One must frequently humble oneself and supplicate to Allah, for He is Modest and Generous, and He draws near to His servant who draws near to Him.