Magento V 1.9.1
>rwd/template/page/html/topmenu.phtml
>add the following code
<?php
$routeName = Mage::app()->getRequest()->getRouteName();
$identifier = Mage::getSingleton('cms/page')->getIdentifier();
?>
<ul id="nav">
<li class="level0 home level-top <?php if($routeName == 'cms' && $identifier == 'home') {echo " active";}?>">
<a href="<?php echo $this->getBaseUrl(); ?>" class="level-top"><span><?php echo $this->__('Home'); ?></span></a>
</li>