pre {
  font-family: sans-serif, helvetica, arial;
  white-space: pre-wrap;       /* css-3 */
  white-space: -moz-pre-wrap;  /* Mozilla, since 1999 */
  white-space: -pre-wrap;      /* Opera 4-6 */
  white-space: -o-pre-wrap;    /* Opera 7 */
  word-wrap: break-word;       /* Internet Explorer 5.5+ */
}

<pre style="font-family: sans-serif, helvetica, arial; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">


I find this useful for wikis and other random one-off posting of text on the internet.
Adapted from http://users.tkk.fi/tkarvine/pre-wrap-css3-mozilla-opera-ie.html
anyall.org