Why does HTML code render correctly in preview but not on
the post?

Why does HTML code render correctly in preview but not on the post? 

-------------------

Answer from Ken Robertson 

The preview tab doesn't run the post through the HtmlScrubber which handles HTML
markup that isn't allowed on the site.  It only processes the main text
modules.

The IFRAME tag is one that is no allowed by the HtmlScrubber with the default
configuration.  If you wish to allow it, see the <MarkUp> section of your
communityserver.config.  For something like that markup, you would need to add
this within the html section of the MarkUp area:

<iframe title="true" style="true" src="true"
/>

Then you'd need to force an app restart to ensure it loads the new settings.