I have a problem with joomla blacklist tags:
'applet', 'body', 'bgsound', 'base', 'basefont', 'embed', 'frame', 'frameset', 'head', 'html', 'id', 'iframe', 'ilayer', 'layer', 'link', 'meta', 'name', 'object', 'script', 'style', 'title', 'xml'

and these attributes:
'action', 'background', 'codebase', 'dynsrc', 'lowsrc'

because joomla omit them!

I want to teach XML, HTML , ... in my site

how can I put some of these tags and attributes like "xml" in my content for my web learning tutorial site?