How many years separated the first and the fourth crusades?

How has mealtime etiquette changed since medieval times? How did people get the news in the medieval times? Did the German name Stepp originate from the name Steppenwolf? Why did the days of the coureurs des bois come to an end? When and which Roman emperor made Britain part of the Roman empire? Why did a medieval millers wear? What where the basic levels from most powerful to least under European feudalism? Cause and effect of the Western Expansion? What role did a master mason play in the medieval times? What is the history of technopreneurship? What is the history and origin of words known as? The goal of the Crusades was? What Marks the beginning of the Gregorian calendar? What is an average size family in the middle ages? Why did all medieval men and women carry a pouch? Where did wearing your jeans below your waist originate? What effect do war migration and trade have on cultural diffusion? How many people can an ancient roman cisium carry? Who began the European trade in African slaves? How did barbarian tribes of Europe influence medieval society?