How to theme a menu in drupal 7 with this html &lt;ul id="nav"&gt;
    &lt;li class="active"&gt;&lt;a href="index.html"&gt;&lt;span&gt;Home&lt;br/&gt;&lt;span class="SousTitle"&gt;The card of flight&lt;/span&gt;&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href="list_news.html"&gt;News&lt;br/&gt;&lt;span class="SousTitle"&gt;The actual &amp; promo&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href="list_compagnie.html"&gt;Compagnies&lt;br/&gt;&lt;span class="SousTitle"&gt;More details&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href="list_airport.html"&gt;Airports&lt;br/&gt;&lt;span class="SousTitle"&gt;Prepare your travel&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href="forum.html"&gt;Forum&lt;br/&gt;&lt;span class="SousTitle"&gt;The community&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
  &lt;/ul&gt;
Use theme_menu_tree() theme function overrides

https://api.drupal.org/api/drupal/includes%21menu.inc/function/theme_menu_tree/7

Copy the contents of 'Code' on these pages to your theme's template.php and change the 'theme' in the function names to the name of your theme, for example: 

function yourcustomtheme_menu_tree($variables) {
  return '&lt;ul class="menu"&gt;' . $variables['tree'] . '&lt;/ul&gt;';
}


Make the changes to the HTML tags, save the template.php and clear caches.

Also if you just want to customize HTML for a specific menu, you can name your functions like this: THEMENAME_menu_tree__MENU_NAME()