This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
For each <tr> tag for your optional rows, add the following:
id="<<put descriptive name here>>" "style="visibility:hidden; display:none"