| Application | Description | Error Code |
| Web Application | An invalid form control with name?is not focusable | -- |
This error appeared when I replaced <textarea> with CKeditor instance and input had a required property.
Because the textarea is replaced by ckeditor, HTML can not find textarea with name=".................".
To solve this, I removed "required" from textarea, so the input element doesn't have the required attribute. And done! Problem solved.