Create a [custom template file][2] node--type.tpl.php where `type` is the machine name of your content type. 

Place it in your theme's template folder and clear/flush the cache to see changes.

Ex: Article content type: **node--article.tpl.php**

    <?php print render($content['field_xxx']); ?>

    // custom html goes here

    <?php print render($content['field_yyy']); ?>

  [1]: https://www.drupal.org/project/markup
  [2]: https://www.drupal.org/docs/7/theming/template-theme-hook-suggestions
  [3]: http://drupal.stackexchange.com/questions/10204/modify-node-in-hook-node-view-for-drupal-7#16620