What's inside "print render($page['content'])"? I want to style my front page in Omega subtheme
The content of the $page array is described in hook_page_alter(), where the documentation says:


  The $page array contains top level elements for each block region:
  
  
  $page['page_top']
  $page['header']
  $page['sidebar_first']
  $page['content']
  $page['sidebar_second']
  $page['page_bottom']
  
  
  The 'content' element contains the main content of the current page, and its structure will vary depending on what module is responsible for building the page. Some legacy modules may not return structured content at all: Their pre-rendered markup will be located in $page['content']['main']['#markup'].
  
  Pages built by Drupal's core Node and Blog modules use a standard structure:

  // Node body.
  $page['content']['system_main']['nodes'][$nid]['body']
  // Array of links attached to the node (add comments, read more).
  $page['content']['system_main']['nodes'][$nid]['links']
  // The node object itself.
  $page['content']['system_main']['nodes'][$nid]['#node']
  // The results pager.
  $page['content']['system_main']['pager']



You can use $page['content']['system_main']['nodes'][$nid]['body'], remembering there is a $page['content']['system_main']['nodes'][$nid]['body'] for each node. Check its structure to see in which way you can add a CSS class to that array.