theme getting wrong when validating a field

Hi
I am having a problem in putting validation. Here is my code.
final TextField PhoneNo= new TextField();
PhoneNo.setMaxLength(10);
PhoneNo.setWidth(145, Unit.PIXELS);
PhoneNo.addStyleName(“h2”);

    PhoneNo
            .addValidator(new RegexpValidator("^[0-9]

{10}$",
“Incorrect Phone number. Valid Phone number contains exactly 10 digits.”));
PhoneNo.setImmediate(true);

and after this i put all fields in gridLayout.
The problem is as the phone number is wrongly put and i move to next button, the PhoneNo textfield goes blackwith description showing on mouse arrow. h2 is a local style of my self generated theme.
Please Help ASAP
D.