I have created a simple WYSIWYG plugin. I have the [plugin-name].inc file in the plugins folder, and the sub-directory with a [plugin-name].js and [plugin-name].css file. The ability to enable the button is available and selected on the WYSIWYG Configuration page, the JavaScript file is being loaded into the edit page, when I click the button I get the behavior I expect, but the css file is not being loaded into the document.

Drupal 7.19, WYSIWYG 2.2.

Comments

Status:Active» Postponed (maintainer needs more info)

Which editor did you try this with? If CKEditor 4, then it's a known issue, please see #1853550-112: Ckeditor 4.0 - The version of CKEditor could not be detected..
Just to be clear, the .css file should be loaded inside the editing area iFrame so it can affect the content in there. Just in case you were looking for it in the main document.

Status:Postponed (maintainer needs more info)» Closed (duplicate)

Without further details about the problem I can only close this issue. Please re-open it if you can provide the requested information. Marking as "duplicate" since it seems likely you tried CKEditor 4 when encountering the issue.