Mix the crushed pretzels with the margarine or butter. Press into a 9x13 pan and bake 10 minutes at 350 degrees F. Let cool. Meanwhile, cream the softened cream cheese with sugar and mayonnaise, then fold in the whipped topping. Spread this over the cooled pretzels. Dissolve the Jello in 2 cups of hot water and add the frozen strawberries. Stir, and then let set slightly. Pour over the cream cheese mixture. Chill and serve.