getting error in membership web.config file

<configuration>
  <connectionStrings>
    <add name="con" connectionString="Data Source=SREEKANTH; Initial Catalog=Northwind; Integrated Security=True"/>
  </connectionStrings>
    <system.web>
        <compilation debug="true" targetFramework="4.0" />
      <authentication mode="Forms">
        <forms name="/.ASPXAUTH" defaultUrl="~/Default.aspx" loginUrl="~/login.aspx" slidingExpiration="true" timeout="20"></forms>
      </authentication>
    </system.web>
</configuration>

There is a problem with your selected data store. This can be caused by an invalid server name or credentials, or by insufficient permission. It can also be caused by the role manager feature not being enabled. Click the button below to be redirected to a page where you can choose a new data store.

The following message may help in diagnosing the problem: Unable to connect to SQL Server database.