The code does not pass because you have placed the comment inside of a header2. You only need to place the comment.
Remember that comments such as <!--TODO: CHANGE FONT SIZE--> are only visible to the coder, which is you and can be used to clear up your code and keep track of it, or add todo’s in this case. There is no need to place them in a Header2 because nobody who visits the webpage will see them: only you will.