Editor does not work in IE11 Quirks Mode.
HTML1300: Navigation occurred.
File: replacebycode-qm.html
HTML1527: DOCTYPE expected. Consider adding a valid HTML5 doctype: "<!DOCTYPE html>".
File: replacebycode-qm.html, Line: 5, Column: 1
SCRIPT5007: Unable to get property '1' of undefined or null reference
File: env.js, Line: 176, Column: 5
SCRIPT5007: Unable to get property 'gecko' of undefined or null reference
File: tools.js, Line: 13, Column: 3
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: dtd.js, Line: 38, Column: 2
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: node.js, Line: 87, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: window.js, Line: 27, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: document.js, Line: 29, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: element.js, Line: 119, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: documentfragment.js, Line: 27, Column: 1
SCRIPT5007: Unable to get property 'createClass' of undefined or null reference
File: walker.js, Line: 153, Column: 2
SCRIPT5007: Unable to get property 'bogus' of undefined or null reference
File: range.js, Line: 373, Column: 2
SCRIPT5007: Unable to get property 'bookmark' of undefined or null reference
File: iterator.js, Line: 81, Column: 3
SCRIPT5007: Unable to get property 'copy' of undefined or null reference
File: filter.js, Line: 10, Column: 3
SCRIPT5007: Unable to get property 'override' of undefined or null reference
File: plugins.js, Line: 22, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: editor.js, Line: 655, Column: 2
SCRIPT5007: Unable to get property 'createClass' of undefined or null reference
File: basicwriter.js, Line: 12, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: comment.js, Line: 30, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: text.js, Line: 31, Column: 2
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: cdata.js, Line: 27, Column: 2
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: fragment.js, Line: 40, Column: 2
SCRIPT5007: Unable to get property 'createClass' of undefined or null reference
File: filter.js, Line: 33, Column: 2
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: htmldataprocessor.js, Line: 530, Column: 3
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: element.js, Line: 121, Column: 2
SCRIPT5007: Unable to get property 'createClass' of undefined or null reference
File: editable.js, Line: 14, Column: 2
SCRIPT5007: Unable to get property 'invisible' of undefined or null reference
File: selection.js, Line: 86, Column: 2
SCRIPT5007: Unable to get property 'bookmark' of undefined or null reference
File: style.js, Line: 70, Column: 2
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: comment.js, Line: 36, Column: 1
SCRIPT5007: Unable to get property '$blockLimit' of undefined or null reference
File: elementpath.js, Line: 11, Column: 3
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: text.js, Line: 43, Column: 1
SCRIPT5007: Unable to get property 'extend' of undefined or null reference
File: skin.js, Line: 169, Column: 2
SCRIPT5007: Unable to get property 'webkit' of undefined or null reference
File: _bootstrap.js, Line: 12, Column: 2
SCRIPT5007: Unable to get property 'isCompatible' of undefined or null reference
File: themedui.js, Line: 244, Column: 3
After deep cache clear I was able to reproduce this issue in major only.