Generally there are two possibilities to preserve unknown XML tags within documents the user is loading into the editor:

First possibility:

• When loading a document that contains unknown XML tags the editor switches to source view and opens a prompt which describes warnings and errors within the document (including the unknown XML tags)
  
• It is not possible to switch to WYSIWYG view until the user corrects the errors and removes the unknown XML tags.

For introducing this editor behavior you have to set following definitions into your config.xml file used:

<cleanupprocess cleanuponload="auto" cleanuponsave="auto" dropillegaltags="<strong>false" />

<documentvalidation enabled="<strong>true" validateonsave="false"  overridedoctype="true" />

Second possibility:

• When loading a document that contains unknown XML tags these unknown tags will be ignored from the CleanUp process and the document validation. This means the tags stay within the source code and the document becomes rendered in WYSIWYG view.
  
• For displaying the unknown tags in WYSIWYG view you should enable the P mode within your toolbar.
  
• Using this method it's not possible to validate documents against a DTD.

For introducing this editor behavior you have to set following definitions into your config.xml file used:

<cleanupprocess cleanuponload="auto" cleanuponsave="auto" dropillegaltags="<strong>false" />

<documentvalidation enabled="<strong>false" validateonsave="false"  overridedoctype="true" />