Another useful feature of Joomla is the ability to have modal windows. This is built into the Joomla core so there is no need for extra plugins and modules. It does offer limited usability but if all you need is to display content (images, html, videos, etc) in a lightbox style modal window then it can be very useful.

In your Joomla 2.5 template find the index.php file and below:

<?php defined('_JEXEC') or die;

Put:

JHTML::_('behavior.modal');

Your template is now ready to display lightbox windows.

To open an iframe in a modal window you would place code like this into your article:

<a class="modal" href="mypage.html" rel="{handler: 'iframe', size: {x: 700, y: 400}}">link text</a>

If you wanted to call an image then you would leave out the rel part of the link:

<a class="modal" href="myimage.png">link text</a>