I've styled my navigation menu with the classes of wp_nav_menu .menu_item , .sub_menu etc.When i added a new page suddenly the whole menu was ruined the classes where changed to .page_item, .children the ul was wrapped with a div container.I checked the code and the function wwas wp_nav_menu...What should I do to get the old menu style?

## Edit

wp_nav_menu( array(
'container' => '',
) );

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Make sure you are calling the correct menu, and a menu was actually set up for that theme_location. –  toscho Oct 30 '13 at 8:48
this way i called the menu –  Antonio Papa Oct 30 '13 at 8:50
Is a menu assigned to that location? –  toscho Oct 30 '13 at 8:54
No, that’s not a problem. It is impossible. –  toscho Oct 30 '13 at 9:10

    wp_nav_menu(array(
'theme_location'  => '',
'container'       => '',
'container_class' => '',
'container_id'    => '',
'echo'            => true,
'before'          => '',
'after'           => '',
'items_wrap'      => '<ul id="%1$s" class="%2$s">%3\$s</ul>',
'depth'           => 0,
'walker'          => ''
));

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This is wrong, you should use a proper theme_location. –  toscho Oct 30 '13 at 10:03
no it doesnt work if i add a theme location :/ –  Antonio Papa Oct 30 '13 at 12:34
What, specifically, doesn't work if you add theme_location? What is the rendered output? What is the expected behavior? What is not happening as expected, or happening unexpectedly? –  Chip Bennett Oct 30 '13 at 12:47
Here is where i found the answer: wordpress.org/support/topic/… i had the same problems –  Antonio Papa Oct 30 '13 at 12:56