//Using connection string in code
        string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["blah"].ConnectionString;


//Declaring the connection string in a config
	<connectionStrings>
		<add name="blah" connectionString="Server=.\sqlexpress;Database=mydb;        Integrated Security=SSPI" providerName="System.Data.SqlClient"/>
	</connectionStrings>

//Server resolving a Url
//dont forget runat="server"
<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="~/login.aspx">Login</asp:HyperLink>