<div class="sidebox">
  <ul id="side-nav">
    <?php foreach ($this->getStoreCategories() as $_category): ?>
    <?php if ($_category->getIsActive()) { ?>
    <?php $open = $this->isCategoryActive($_category); ?>
    <?php $potential = $_category->hasChildren(); ?>
    <li class="subcat">
      <a href="<?php echo $this->getCategoryUrl($_category); ?>"<?php if($open) { echo ' class="open"'; } ?><?php if($potential) { echo ' class="potential"'; } ?> ><?php echo $_category->getName();?></a>
      <?php if ($open && $potential): ?>
      <ul id="sub-sidenav">
        <?php foreach ($_category->getChildren() as $subcategory): ?>
        <?php $subCat = Mage::getModel('catalog/category')->load($subcategory); ?>
        <?php $open = $this->isCategoryActive($subCat); ?>
        <?php $potential = $subCat->hasChildren(); ?>
        <li>
          <a href="<?php echo $this->getCategoryUrl($subCat); ?>"<?php if($open) { echo ' class="subopen"'; } ?><?php if(!$potential&&$open) { echo ' class="final"'; } ?> ><?php if($potential&&$open) { echo ' '; } elseif($potential) { echo ' '; }?><?php echo $subCat->getName(); ?></a>
          <?php if ($open && $potential): ?>
          <ul>
            <?php foreach ($subcategory->getChildrenCategories() as $subsubcategory): ?>
              <?php $subsubCat = Mage::getModel('catalog/category')->load($subsubcategory); ?>
              <?php $open = $this->isCategoryActive($subsubCat) ?>
              <li><a href="<?php echo $this->getCategoryUrl($subsubCat); ?>" <?php if($open) { echo ' class="final"'; } ?>><?php echo $subsubCat->getName(); ?></a></li>
            <?php endforeach; ?>
          </ul>
          <?php endif; ?>
        </li>
        <?php endforeach; ?>
      </ul>
      <?php endif; ?>
    </li>
    <?php } ?>
    <?php endforeach ?>
  </ul>
</div>