hello
how to add affix function bootstrap on mainnav ?
i use t3 v1.4

i am here but it doesn't realy works ...
in mainnav.php

<div data-offset-top="0" data-spy="affix">

      <div class="nav-collapse collapse<?php echo $this->getParam('navigation_collapse_showsub', 1) ? ' always-show' : '' ?>" style="z-index:100000000;">

      <?php if ($this->getParam('navigation_type') == 'megamenu') : ?>

        <?php $this->megamenu($this->getParam('mm_type', 'mainmenu')) ?>

      <?php else : ?>

        <jdoc:include type="modules" name="<?php $this->_p('mainnav') ?>" style="raw" />

      <?php endif ?>

      </div>

    </div>

  </div>

  </div>

</nav>

the menu is fixed but not on top
http://legribouillard.com/newgribou/
what i lost ?