You are so right, thank you!!!! I removed the comments and it is now on page one (and it is only 1kb of size)
(also any other comments on my code or structure would be much appreciated - without taking up much of your time of course)
However, the mystery is not solved yet for me, because all the comments were actually copied from Jellby's cover of "The Prince and the Pauper", and this cover was on page one all right.... I really don't understand why they would behave differently. I had kept the commented code because I thought I might need it if I wanted to edit the cover, but I can see now that it is best to keep the cover.xhtml as small as possible. But...again...why did Jellby's cover work fine and mine didn't, when it was actually only a copy of his? Oh well...