custom page is wordpress standalone page which is not use as wordpress page or page.there is some situation where you need custom page which will define owns html and js

and othere elements using wordpress header and footer.This is very easy in wordpress to create cusom page.This wordpress custom page will depends on theme you are using.So some of customization need on given code.You have to put these custom page into root of your wordpress site.

<?php
define('WP_USE_THEMES', false);
require('wp-blog-header.php');
get_header();
?>

<div id='page'>
<div id="post">
<b>This wordpress page</b>
</div>
</div>

<?php
get_sidebar();
get_footer();
?>

Here sidebar and inner html are dipends on there setting.So do settings according.