php yii framework :: $content is not found

renderPartial("/site/_navigation",null,true,false); ?>

    <div class="content">

    <?php echo $content; ?>

     </div> 

      <?php echo $this->renderPartial("/site/_footer",null,true,false); ?> 

this is my code.

there is variable in code $contant.but i cant able to find the variable anywhere.

pls help me