Solution for Error 26 - Error Locating Server/Instance Specified?

I have published my website http://www.theyuvaworld.com for my college project but it is showing

Error 26 - Error Locating Server/Instance Specified. Other things are working properly.

You can visit website for detailed Error.

My project is C# ASP.NET 4.0 and built in Sql Server 2008 of Visual Studio 2010.

I am using this connection string in every page.

SqlConnect开发者_如何转开发ion con = new SqlConnection("data source=.\\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true");
SqlCommand cmd = new SqlCommand();

I know I can put it in Web.config but I don't know how to use it in aspx pages for queries?

My Question is : What changes should I do in my Connection String to get my website working.

Other details : I have taken my Web Hosting Plan from http://www.hostingfarms.in and it supports Sql Server 2008.

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Try to work around this piece of code .Username and password should be supplied in get connection string if you are using sql authentication

private static void OpenSqlConnection()
{
    string connectionString = GetConnectionString();

    using (SqlConnection connection = new SqlConnection())
    {
        connection.ConnectionString = connectionString;

        connection.Open();

        Console.WriteLine("State: {0}", connection.State);
        Console.WriteLine("ConnectionString: {0}",
            connection.ConnectionString);
    }
}

static private string GetConnectionString()
{
    // To avoid storing the connection string in your code, 
    // you can retrieve it from a configuration file.
    return "Data Source=MSSQL1;Initial Catalog=AdventureWorks;"
        + "Integrated Security=true;";
}