How to access Div tag in Asp.NET Themes and Skins

you can use <asp:panel, it will become <div> after rendering.

Try this

skinfile.skin  inside App_Themes/Theme1 folder

<asp:Panel runat="server" SkinId="panelSkinned" BackColor="Red" ></asp:Panel>
yourpage.aspx
<%@ Page Language="C#" AutoEventWireup="true" Theme="Theme1" ...
<asp:Panel ID="test" SkinID="panelSkinned" runat="server" >
hello hai........ :)

</asp:Panel>

html after rendering(yourpage.aspx) :

============================

<div id="test" style="background-color:Red;">
 
        hello hai........ :)
  </div>

Hope this may help