If you adding pages in admin area the link will be like

sitename/pages/test.html.

It also show the same theme.But You can't add script code page in admin area.

If you need you can create a new php page.

Create a test.php with the following


Code:
<?php

include("include/config.php");
include("include/function.php");
include("include/language/$language/language.php");
STemplate::display('header.tpl');
STemplate::display('test.tpl');
STemplate::display('footer.tpl');
?>
and also make test.tpl (template folder) page and add the content.

Add test.php link in header.tpl(template folder) file.

Check its ok or not