Please use the following code:

 

function CE_attachEvent()
   {
    // get the cute editor instance
    var editor1 = document.getElementById('<%=Editor1.ClientID%>');
    
    //Get the editor content 
    var editdoc=editor1.GetDocument();

    // attach Event
    if(editdoc.attachEvent)
     editdoc.attachEvent('onkeypress',HandleChange);
    else if(editdoc.addEventListener)
     editdoc.addEventListener('keypress',HandleChange,true);
   }   
   
   function CE_detachEvent()
   {
    // get the cute editor instance
    var editor1 = document.getElementById('<%=Editor1.ClientID%>');
    
    //Get the editor content 
    var editdoc=editor1.GetDocument();

    // detach Event
    if(editdoc.detachEvent)
     editdoc.detachEvent('onkeypress',HandleChange);
    else if(editdoc.removeEventListener)
     editdoc.removeEventListener('keypress',HandleChange,true);
   }
   
   function HandleChange()
   {
    // get the cute editor instance
    var editor1 = document.getElementById('<%=Editor1.ClientID%>');
    //Get the editor content 
    var editdoc=editor1.GetDocument();
    alert(editdoc.body.innerHTML);
   }