Is it possible to publish a paper on a topic about which you already wrote an online article?

I am a student and so I have no experience in publishing papers and I do not know much about it. My question: Is it necessary for publishing a paper in a journal, that you never have published something similar on your homepage / blog or on another online project?

I have the feeling that this is not a problem, because the own written online article on the personal blog was never peer-reviewed and publishing papers based on a dissertation does not seem to be a problem. Am I right?