Ok so I sorted out that issue myself, I had specified two doctypes in my page.ss

But since using the code the page shows up and the items are displayed, but I can no longer get into the page through the CMS. I get an empty box pop up with a button on it with no text and then it says in the bottom left Error

Not sure why this is happening

The controller goes in the same file as the model.

TestimonialPage.php

class TestimonialPage extends Page {}

class TestimonialPage_Controller extends Page_Controller {}

This is all very fundamental stuff covered in the first tutorial in the docs. I would recommend reading up on that.

As far as the XML parsing error, I would avoid using an XML doctype. They're nothing but a headache. Stick to XHTML 1.1 transitional.

As for that empty error message, I'll say one more time, you need to turn on error reporting. You're going to drive yourself crazy trying to debug without error reporting turned on.