Cool 404 adaptive page template.
Installation for the default template, but below in the description there is an instruction on how to customize the template for yourself.

Installing a 404 Error template in your template:

Files from default need to be thrown into your template.
Go to the folder /your template/assets/errors/, open the file there notfound.tpl.php , in line 17, replace <link type="text/css" media="all" href="<?php echo $config->root; ?>templates/default/css/404/style.css" />, on <link type="text/css" media="all" href="<?php echo $config->root; ?>templates/folder name of your template/css/404/style.css" />, also the line (19, 20, 49, 58,75,76,77) in them, too, replace the name of the default folder with the name of your template.
Next, open /your template /css/404, there we open the style.css file, in it we change the name of the default template folder in lines (181, 191, 233) to the name of your template folder.
After that, we go to your site and in the line after your_domain .ru/, we write abracadabra and get a new page 404