problem with include_blank


I've got a 'easy' question. I have a formular with a datetime field and
I want blank field with a white space - char because the normal way with
:include_blank is not w3c - conform. Has anyboy an idea?

I use this but it don't fit:

<%= f.label :unpublished_on, "#{:unpublished_on.l}:" %>
<%= f.datetime_select :unpublished_on,
                    :use_month_numbers => true,
                    :minute_step => 15,
                    :include_blank => "&nbsp;", # <-- this one
                    :order => [:day, :month, :year]

Regards, Eddy