I am doing ajax post to post the data from javascript in mvc4 but it fails with following exception
string exceeds the value set on the maxJsonLength property.
Parameter name: input
System.ArgumentException: Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property. 
I have already tried setting the configurations in web config but it is not working
<system.web.extensions>
    <scripting>
        <webServices>
            <jsonSerialization maxJsonLength="2147483647"/>
        </webServices>
    </scripting>
</system.web.extensions>  
I also tried below link but nothing works: http://forums.asp.net/t/1751116.aspx?How+to+increase+maxJsonLength+for+JSON+POST+in+MVC3
var editorText = eval(htmlEditor).GetHtml();     
$.ajax({type: 'POST',
    cache: false,
    contentType: 'application/json; charset=utf-8',
    url: "../Home/SaveExceptionLetter",
    data: JSON.stringify({ message: editorText }),
    datatype: 'json',
    success: function () {
    });
} });
[HttpPost]
[ValidateInput(false)]
public void SaveExceptionLetter(string message){
    //processing this message
}
string exceeds the value set on the maxJsonLength property.
Parameter name: input
System.ArgumentException: Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property.
Parameter name: input
   at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit)
   at System.Web.Mvc.JsonValueProviderFactory.GetDeserializedObject(ControllerContext controllerContext)
   at System.Web.Mvc.JsonValueProviderFactory.GetValueProvider(ControllerContext controllerContext)
   at System.Web.Mvc.ValueProviderFactoryCollection.<>c__DisplayClassc.<GetValueProvider>b__7(ValueProviderFactory factory)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Web.Mvc.ValueProviderFactoryCollection.GetValueProvider(ControllerContext controllerContext)
   at System.Web.Mvc.ControllerBase.get_ValueProvider()
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor)
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState)
 
     
     
    