Check out this list to find the lightbox for you.
Which Lightbox is right for you? | etc: a stream of web dev and design consciousness
However, I later came across Fancybox which seems to cover all bases of what type of content may appear in your lightbox. Their download contains a great demo that is easy to dissect and learn how to integrate it with your site.
The content may be an image, an external web page, HTML, Flash etc.
I used fancy box many times.
I glad to use it.
It shows youtube videos in popup too
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