The <pre> tag is the best way to post chords, but it does not make line breaks. And if you don't have line breaks put in manually or automatically, you'll have an 'orrible mess.
If your material already has line breaks in it, make sure the "automatic linebreaks" feature is turned OFF. Leave it ON is you're copy-pasting a straight text file, with no line breaks or HTML tags in it.
Be sure to close the preformat tag with </pre> at the end of the section with the chords.