[Theme Horse Support Team]

Hi jeanlucgarnier,

There is no any documentation available to customize 404 page. We have already replied on forum to customize 404 page using child theme. You can also search on forum. What you need to do is create child theme with two file (style.css and functions.php)

This is an example how to unhook page 404.php and use your own content.
First of all you need to unhook the functions and then only customize the code in your child theme functions.php. Here is a simple example how to unhook functions and customize the code. Below code should be added inside functions.php of child theme.

// Unhook default Thematic functions
function unhook_thematic_functions() {
    // Don't forget the position number if the original function has one

remove_action( 'attitude_404_content', 'attitude_display_404_page_content', 10 );

}
add_action('init','unhook_thematic_functions'); // removes the header content by using hook attitude_header

add_action( 'attitude_404_content', 'attitude_child_display_404_page_content', 10 );
/**
 * function to show the footer info, copyright information
 */
 
 
function attitude_child_display_404_page_content() {      ?>   
<div id="content">
		<header class="entry-header">
			<h1 class="entry-title"><?php _e( 'Error 404-Page NOT Found', 'attitude' ); ?></h1>
		</header>
		<div class="entry-content clearfix" >
			<p>Thank you</p> 
		</div><!-- .entry-content -->
	</div><!-- #content -->
  <?php 
}

Thank you!