If you meet an error with your TinyMCE as Incorrect function. setActive on IE11, it seemly, you are using one of an old version of TinyMCE in 2013, there are some places already raised the error in their old product such as: https://core.trac.wordpress.org/ticket/25281 https://github.com/tinymce/tinymce/commit/cd01160b037cab69c2f45866d9443e09851cf839 http://www.tinymce.com/develop/changelog/?type=tinymce That would explain the issue. So, please upgrade your TinyMCE…