ConnectionStrings or appSettings in Asp.net
Though you have shifted to ASP.net 2.0 or later then why in your application you are still storing connection Strings in AppSettings ?
Here is sample code to access connectionStrings.
<add connectionString="servr=.;uid=sa;password=pass;database=mydb" name="XYZConnectionString" providerName="System.Data.SqlClient"/>
In code behind you can access it like this.
string connection = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["XYZConnectionString"].ConnectionString;
Benifit of adding connectionString in connectionString section is, you will be able to configure your ASP.net membership provider , custom provider and third party components.
To know which connction string to use for what DB provider, you can refer www.connectionstrings.com
Note*: If you are using Class Library project in your ASP.net project and your library project needs to access connection string,
you need to add refrence of System.Configuration in your class library project.