getSubmittedValue() is coming null jsf

getSubmittedValue() is coming null jsf

I facing one problem in jsf, when i attached to my , as shown below
<h:inputText id="" value="" binding="">
<a4j:support
actionListener="Action_Class.validateUserName"
event="onblur" />
</h:inputText>
As shown in above, when i am tabbing out from field, validateUserName has
to call.it is calling,but when i am trying to get my submitted value as
shown below, null is coming. UIInput input = actionEvent.getParent();
String userName = input.getSubmittedValue(); username is coming as
null.(The submitted value is coming only in IE browser, but in remaining
browsers i am getting null as submitted value). Kindly do needful.