I have a problem with generated content within tables. We use some in-house developed software that generates html dynamically. The dynamic content is marked up inside a special tag that we designed. So I have a hard coded table begining with a specified width and within the table some rows are inside our own tag called <CALC>, eg

<table style="width: 600px;">
<CALC>
<tr>
   <td class="center">May</td>
   <td class="center">31</td>
   <td class="left">Balance</td>
   <td>&nbsp;</td>
   <td>&nbsp;</td>
   <td>&nbsp;</td>
</tr>
</CALC>

This looks fine as a web page since the browser ignores the unknown <CALC> tags. The issue I am having in prince is that it does not apply the table formatting across the <CALC> tag. Can I do anything for this?

You could make the CALC element a table row group, as if it were a tbody element:

CALC { display: table-row-group }

That should stop it from interfering with the table rendering.