As described here:
http://forum.dokuwiki.org/thread/4787
Tested in browsers: Firefox 3.0.17 & Opera 10.00 on Ubuntu Linux
HTML causing whitespace:
<div id="picker0" class="picker pk_hl" style="position: absolute; margin-left: -10000px;">
</div>
<div id="picker1" class="picker" style="position: absolute; margin-left: -10000px;">
</div>
<div id="picker2" class="picker" style="position: absolute; margin-left: -10000px;">
This is only relevant when editing pages except for users that have the discussion plugin installed.