Sabrina,

The IE10 emulation of IE11 is different from real IE 10.

Can you try Cute Editor new build? It works fine in IE 11. 

If it works for you, please download the latest build.

http://cutesoft.net/example/general.aspx  

asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx