<p>What is the best way to dynamically add TableRows and TableCells to an ASP.NET table from Javascript?</p>

<p>Thanks,</p>

<p>Jeff</p>

Your question is too vague to answer completely, I'm afraid.  If you actually want to create TableRow or TableCell objects, you would of course need to post back (no need for JavaScript) or make an AJAX call (JavaScript) to server-side code.  Either way, it's not really JavaScript doing the work.  If you just want to dynamically add a row to an HTML table presented in the browser, you could accomplish this without any need for TableRow/TableCell abstractions from ASP.NET.
For a more complete answer you'll have to be more specific about what you are trying to accomplish.