Why did Henry IV meet Pope Gregory VII at Canossa?

In the course of the Investiture Controversy, Henry IV had be excommunicated. In order to have the ban lifted, he went to see the Pope at Canossa to do penance. He stood in the snow three days, begging to be forgiven. Popular legend has him doing this barefoot. He was forgiven, but required to meet certain conditions, which he violated, and the problems continued.

There is a link below to an article on the Investiture Controversy.