cascading style sheet error in asp.net application

Question

 

<%@ Page Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Default2.aspx.vb" Inherits="Default2" title="Untitled Page" StylesheetTheme ="StyleSheet.css" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

<asp:Label ID="Label1" runat="server" Style="z-index: 100; left: 300px; position: absolute;

top: 600px" Text="Welcome To My Website"></asp:Label>

<h1 class ="center" > testing </h1>

<p class ="center">testing</p>

</asp:Content>

 stylesheet code:

/////////////////////////////////

body {

}

h1,h2,h3,h4,h5,h6

{ color :Red }

p.right{ text-align :right}

p.center{ text-align :center }

.center{ text-align :center }

 

when i run this application ,i geeting this error

Parser Error Message: Theme 'StyleSheet.css' cannot be found in the application or global theme directories.

Source Error:

Line 1:  <%@ Page Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Default2.aspx.vb" Inherits="Default2" title="Untitled Page" StylesheetTheme ="StyleSheet.css"   %>
Line 2:  <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
Line 3:      &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;

plz help me..............