Visural wicket, input text hint is considered as input value.

Hello,
I don't know if here is the right place to ask this question, but visural
wicket group seems to not be active anymore.
I used visural wicket library to display hint into a text field. When
submitting the form by an ajax button, the component is properly handled.
But when I use a AjaxFormComponentUpdatingBehavior("onblur"), when the
component is validated, the hint is considered input text.
Example, for a text field for age, teh text 'Please enter your age' is
considered as input text. After rendering, the text is not styled as a hit
anymore.
I could not figure out what is different between the two ajax request
(submit button and ajaxformcomponentupdatingbehavior)

Thanks.