AJAX/php - Plugin Cross Site Request

I've recently been working on a small AJAX/PHP plugin, its very easy to understand, you just call the page and it returns a quote from a database in html, something like

<strong>quote here.. <em>author name</em></strong>

And then you style it however you want, its good for semantics that way, you would typically wrap it in a div and update that div with the output each time from your ajax.

It all works fine, and you can see an example here @ www.theshadownest.com.au click on the clock, and you will see the quote come up. disregard the other stuff in the box.

The idea i had for this was set up a large database of quotes with simple semantic output and let Ajax queries call that page, but i want to be able to call that page output from other servers, urls etc... I thought that would be fine, you just request the page with ajax on your site and it could return the response from my site...

But this does not work, you get a permission denied error in the Javascript, it obviously can't do this.

How do you write a PHP/AJAX plugin that can work from multiple sites, because i want to be able to let anyone make a request, its basically a resource for people who want to add quotes to their site without setting up their own database or writing their own php.