Comment 4 for bug 76604

Instead of alternating, I would suggest converting consecutive spaces to all   except the last one:
  word_____word -> word    _word
(so that the browser never wraps before a   leading to misalignment).

Or, you could forget &nbsp; entirely and just use <p style="white-space: pre-wrap" /> or <pre style="white-space: pre-wrap" /> to solve the horizontal scrolling problem:
  <http://www.w3.org/TR/CSS21/text.html#white-space-prop>
  <http://labnol.blogspot.com/2006/10/html-css-trick-for-displaying-code.html>