In joomla articles is not allowed to insert an iframe because it belongs to a blacklist of tags that are filtered. When you try to add one of these tags, it's automatically removed....it's a very useful security policy and we reccomend to don't disable it.

anyway if you have the need to use an iframe like the deepzoompix in the previous article...you can use this workaround :

1) install the full pack Jumi

2) build an html file with only the iframe that you need and put it on your web server. You need to do this because Jumi work only with local files.

3) in the joomla article use a snippet like this one : 

{jumi incl[yourfile.html] width[180px] high[430] scroll[no]}