CSS selectors in nested id/class situation

My website works this way:

<div id="sb-site"> <!-- main website div -->
  <div class="content"> <!-- the content div -->
    <div class="box1"> <!-- the posts div container -->
      <div class="box2"> <!-- a div to style some og the post content -->
      ...some content here
      </div>
      ...some other content here
    </div> <!-- box1 ends here -->
    <div class="navigation>
      <div class="alignright"><?php next_posts_link('Next Entries &raquo;','') ?></div>
    </div>
  </div> <!-- the content div closes here -->
</div> <!-- end of the website / there is a menu in a sidebar inside another div later on -->

I cannot figure out the CSS. Nothing works so far. Any good pointers?

https://wordpress.org/plugins/infinite-scroll/