[Jellby]

Originally Posted by ATDrake

Mind you, I wouldn't bother putting display: block on the the <span>s, since the <br>s accomplish the task of visually separating them, and I think a hanging indent is best handled by using a negative text-indent value on the containing block.

I think you are not addressing the core problem. Having poetry lines is easy, the tricky thing is having each line wrap independently and with a hanging indent when the block width is small. For example, this verse:

'You are old, Father William', the young man said,
  'And your hair has become very white;
And yet you incessantly stand on your head--
  Do you think, at your age, it is right?'

should display as four lines, 2nd and 4th indented (but this indent is not the problem we are dealing with now), if the width is sufficient. But if the screen is narrower, it could be something like:

'You are old, Father William', the young
                man said,
  'And your hair has become very white;
And yet you incessantly stand on your
                head--
  Do you think, at your age, it is right?'

Note the 1st and 3rd lines are now wrapped, with a large hanging indent to clearly mark their second parts as belonging to the same verse line (in some cases/countries/traditions, the second parts should be right-aligned instead).