OK, apparently what I posted was BS - I was following the instructions at http://www.mobipocket.com/dev/articl...guidelines.htm
Which states: "Boxes & Important information display
Use a <div> tag with e.g. a light red background color and a border="1" attribute to highlight a paragraph. "
Once I stripped out my CSS and used their suggestion, it doesn't work in either Firefox or Epiphany - and so of course it wouldn't work when converted to MOBI.
Any suggestions on how to get a border and background around a block of text in HTML that will convert to mobi (CSS doesn't stay, and using a table doesn't work if the text goes off the 'page').