function isEmpty(aTextField) {

   if ((aTextField.value.length==0) ||

   (aTextField.value==null)) {

      return true;

   }

   else { return false; }

}

		function checkForm(form){

    if( isEmpty(form.FirstName) ){

        alert( 'First Name is required field!' );

        return false;

    }

    if( isEmpty(form.LastName) ){

        alert( 'Last Name is required field!' );

        return false;

    }

	if( isEmpty( form.PhoneNumber ) ){

        alert( 'Phone is required field!' );

        return false;

    }

    if( isEmpty( form.Email ) ){

        alert( 'Email is required field!' );

        return false;

    }



    return true;

}