That's O.K. as long as the student agrees and you don't make a habit of it. But remember, learning is easier when you are there every day. When you know you will be absent, let your professor know in advance. Depending on the size of the class, you may choose to do so by a written note delivered to the professor's office, a phone message, or in person at the end of a class period. Sit near the front.
Studies indicate that students who do so tend to earn better grades.
You'll find that most of your comments will be appreciated. See your professor outside of class when you need help. Professors are required to keep office hours for you. If possible, make an appointment. Doing so will make the conference more convenient for both parties.