With Calibre 2.0, the E-Book Viewer is displaying an extra space between some words in ePubs when I have the serif font set to Constantia (or Century or Century Schoolbook etc). When set to Times New Roman these extra spaces disappear. Using the editor, I can tell these spaces always occur when things like:
<a id="page_281" class="calibre1"></a>
appear. I speculate that perhaps the viewer is replacing this with a zero-width space character? And that some fonts incorrectly display this as a non-zero width space? I suggest either dropping the zero-width character entirely or at least giving the user an option to drop it.
With Calibre 1.47 these epubs looked fine.
Windows 7 SP1