I have empty pages waiting for your words and pictures. What am I?

I sit on your head but have no eyes. I keep you warm when it's cold outside. What am I? Solve the riddle → I have four legs and eat grass. I give milk that you can drink. Solve the riddle → I am cold and sweet. I melt if you don't eat me quickly. Solve the riddle → I have many small carriages, but no real passengers. You push me around and hear my soft squeak. Solve the riddle → What has squares but is not a window? Solve the riddle →