Yes, the weight of the cart and the material in the cart must not exceed 45 kg (100 lbs.) for a small cart, 90 kg (200 lbs.) for a medium cart or 115 kg (250 lbs.) for an extra-large cart.
If you can easily roll your cart, it is likely not overweight. If your cart is too heavy, remove some material and save it for your next collection day. If you are putting heavy material in your cart such as apples that have fallen from your trees or wet leaves in the spring, you may want to fill your cart only half full.