css work in design view.but not at run time?

<%@ Page Title="" Language="C#" MasterPageFile="~/Inner.Master" AutoEventWireup="true"
    CodeBehind="Permission.aspx.cs" Inherits="Etranscribe.Contents.USERS.ADMIN.Permission" %>

<%@ Register Src="~/Contents/UserControls/Header.ascx" TagName="HeaderControl"
    TagPrefix="uc1" %>
<%@ Register Src="~/Contents/UserControls/Footer.ascx" TagName="FooterControl"
    TagPrefix="uc1" %>


    

<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">
    <style type="text/css">
       
    .chkChoice input 
   { 
       margin-right: 30px; 
   }
    
   
    </style>

</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<fieldset>
   <legend>Fax </legend>
       <table border="0" width="100%">
               <tr>
                <td>
                    <asp:CheckBox ID="ChkBoxFaxSearch" runat="server" CssClass="chkChoice" Text="Fax Search" onClick="SetUserTypeCheckBoxValues(this)" />
                </td>
               </tr>
</table>
</fieldset>
</asp:Content>