Related: Edit CSS
The feature must be enabled through:
Look and Feel -> Theme -> tick edit templates then apply.
(once this is done you will see "Edit templates" in your Admin menu)
The user must have the tiki_p_edit_templates permission.
Smarty template files (.tpl) of your theme via the web interface.
It is also possible to let users view templates without editing
Registered users can try here:
Possible Explanation - Some shared hosting companies have built-in security that prevents certain files from being executed. If you received an error similar to this when installing TikiWiki the same solution likely applies.
Solution - Contact your host and have them 'whitelist' or allow the file tiki-edit_css.php to be executed.