Non-Drupal pages

Hello Guys,

I am using multisite configuration. All my domains are on Hostgator cPanel's parked domain.
Each domain is defined in "sites" folder.

My problem - how to create non-Drupal pages within Drupal installation? Let say I wanted to manually create a separate sales page or download page under the same domain without using Drupal's "create content".

Yes, have tried Drupal forum but failed to find related post. Let me try to illustrate it below.

main site/domain: www.mainsite.com
parked domain: www.example.com

sales page: www.example.com/sales.php
download page: www.example.com/download.php

So now, how do I insert this page into the site. Please help.

Thanks in advance.

Hilmy
I-m-no-coder