One thing I noticed when adding my own styles to any instances of HTMLEditor in my sites was that the styles almost certainly won't show up in my editor until I have cleared my browser's cache file. That had me stumped for quite a while.
And this from an older post:
"Also worth looking out for is that if your PowerCMS folders and files are all in the root directory and NOT in their own folder in the root directory (i.e. 'CMS', 'PowerCMS' or 'CMS102'), then re-entering the HTML Editor UI and making changes is fine, go ahead. HOWEVER, if your PowerCMS files and Folders - including the HTML Editor folder - are in their own folder within the root folder of your site, then making changes through the Editor UI will just create a new HTML Editor folder in the root directory of your site and really confuse matters.
How to get round this:
Go to 'Manage your Sites' in the DreamWeaver menu ('Sites'). Select your site and create a duplicate. Click 'Edit' to edit your duplicate site. Change the local and testing server paths for Local Root Folder, Testing Server Folder and (Testing Server) URL Prefix to the folder that contains the PowerCMS files and folders. For Instance, all references to these folders in my site that are currently: C:\Inetpub\wwwroot\Pictuality\ would become C:\Inetpub\wwwroot\Pictuality\CMS\.
In the Local Info screen for 'Site Name' just add the suffix 'CMS' to your site name, and save the site definition. Now (and whenever you want to), using this site definition, you can re-enter the HTML Editor UI and make changes without HTML Editor creating a new directory and big problems."
FCKConfig.EditorAreaCSS = '../../css/myownstyles.css'; // relative to fckeditor/editor/fckeditor.html
FCKConfig.StylesXmlPath = '../custom/contents_update_ContentValueStyles2.xml'; // relative to fckeditor/editor/fckeditor.html
If you see these changes, then your styles have been added. (Remember to clear your browser cache!). If you don't see these changes, then it is likely that your PowerCMS files and folders are in their own folder, and HTMLEditor has created a new HTMLEditor folder in the root directory.