Remove /en/ extension in default URL in Joomla

Do as following: Go to Plugins -> Language Filter and set Yes to: Remove the prefix from default language.

How to enable iframe code for the TinyMCE Editor in Joomla

To enable Iframe code for the Tiny MCE Editor, go to Extensions -> Plug-in Manager -> Editor – TinyMCE. Open it, than find “Prohibited Elements” area.

Now you can remove “iframe” tag from this list of prohibited elements. At the end be sure to save your changes when you’re done.

How to enable iframe code for the JCE Editor in Joomla

Navigate to components -> JCE -> Editor Profiles -> Default -> Editor Parameters -> Options to access these options.
In the Edit Profile area for the Default editor, click on the Plugin Parameters Tab, and then click on the “Media Support” tab. Than enable “Allow Iframes” setting option to “Yes”.

Next, select “Save & Close” when your done.

How to remove HTML filtering in JCE in Joomla

The popular JCE editor has a few options focused on HTML filtering and output: Validate HTML and Doctype selection, which can be found in the “Editor Global Configuration” tab or inside the available profiles’ settings. Navigate to components -> JCE -> Editor Profiles -> Default -> Editor Parameters -> Options to access these options.

Please check also “Advanced” tab where you can set which elements are allowed and which are not. Check that the Allow Javascript or Allow CSS or Allow PHP options are set to Yes – depending on which code type you need to insert.