Hanuman stands for extraordinary physical strength, courage and humility. Above all, he is known for his devotion to Rama. So, it was little wonder that Rama entrusted Hanuman with the task of carrying his message to Sita in Lanka.
Vishnu, they say, is just one of a powerful threesome - the highest lords of the universe. However, though Brahma created the universe and Shiva can destroy it, it is up to the great god Vishnu to keep all creatures within well and happy.