Datagrid CSS not work..

[Wasco]

Hi,
I created a CSS StyleSheet like this:
---------------------------------------------------------------------------------
..gridDetail
{background-color: #DBD3C1; width:952px;
font-size:x-large; }
..itemStyle
{ color:#4A3C8C;
background-color:#E7E7FF;
font-family:Verdana; font-size:xx-large
}
..headerStyle
{font-weight:bold; color:#F7F7F7;
background-color:#4A3C8C;}
---------------------------------------------------------------------------------

and a datagrid using that CSS file:
---------------------------------------------------------------------------------
<asp:datagrid id="DataGrid1" runat="server" CssClass="gridDetail">
<AlternatingItemStyle CssClass="alternate"></AlternatingItemStyle>
<ItemStyle CssClass="itemStyle"></ItemStyle>
<HeaderStyle CssClass="headerStyle"></HeaderStyle>
</asp:datagrid>
---------------------------------------------------------------------------------

but it doesn't work.
I create columns of datagrid at runtime.

Could you help me please?

Sorry for my english.

Thanks a lot in advance
wa