Trouble With My 1st Connection

 Using Vs2005 sqlServer 2005

When i try to connect i get this error:
An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Connection string:
<connectionStrings>
<add name="pubsConnectionString1" connectionString="Data Source=.;Initial Catalog=pubs;User=mk;pw=x"
providerName="System.Data.SqlClient" />
</connectionStrings>

Calling code :

try
{
using (SqlConnection cn = new SqlConnection(WebConfigurationManager.ConnectionStrings[0].ConnectionString))
{
cn.Open();

}

}
catch (Exception ex)
{
Response.Write(ex.Message);
}