We often embed Vimeo videos into Joomla 2.5 websites without any issues, but I am currently working on a site that insists on removing the iFrame tags.
This is happening whether I am using the RokPad editor (our default), codemirror, or NO editor. It absolutely seems to be related to some Joomla HTML filtering that I can't isolate. For grins I changed the <iFrame> tags to <a href> tags and the code survived the save, just fine.
I am running AdminTools. I thought maybe there was some configuration in the WAF setting that was filtering html. I couldn't find anything.
UPDATE:
I figured this out. In the global config, under Text Filters, I needed to set super users to No Filtering, as the Default Black List filters out iFrame tags.
I'm fighting the urge to delete this post to hide my shame and chagrin, but I figure there will be others who can benefit from this lesson.
I tried disabling magic quotes, using several editors (JCE, tiny, rokpad or "no editor" option), configuring JCE to accept iframes, doing everything you say here in the forums and nothing works...it keeps stripping the html code. I was using "no filtering" in user configuration for superuser but it didn't work.
Finally, what worked was using "custom black list" and writing fffffff or whatever. It finally worked for me! I hope it works for someone else.