Between the following couple of sentences, which one is right? Or better ask, which one is more right if both are right.
A: A keyword can not contain more than three words.
B: A keyword can contain no more than three words.
I'm an English learner, thus it ain't my mother tongue. So please feel free to teach me everything you think is needed. If there are any differences in meanings, mention it. If there is any preference to use each sentence (or other sentences you may suggest), tell my why.