Enabling Users to Personalize Themes in ASP.NET 2.0

You can use themes to enable the users to further personalize your application.If you store the name of the preffered theme for user in the user's ASP.NET profile,you can programatically set this theme as each page loads.You must set the theme during the Page_PreInit event handler or earlier,
VB
Sub Page_preInit(ByVal sender As Object , _ByVal e As System.EventArgs) _
            handles Me.PreInit
       Page.Theme = Profile.PreReferredTheme
End Sub
C#
void Page_PreInit(object sender , EventArgs e)
{
           Page.Theme = Profile.PreReferredTheme ;
}