Can I use this Script on HTML webpages ?
Yes you can, as long as your server has PHP & .htaccess support. Please make sure that you hosting provider allows you to execute HTML files as PHP . Incase your hosting provider does not provide the option of executing HTML files as PHP , you have a work around
Rename your .html file to .php & Add this to your .htaccess and change the index.html to index.php
RewriteEngine On RewriteRule ^index.html /index.php [L]
This way you will maintain the same link & your SEO would not be affected either.