Hi,
use this in the web.config file.
<connectionStrings>
<add name="MedVisitConnectionString" connectionString="Data Source="";Initial Catalog="";User ID="";Password=""" />
<remove name="MedVisitMembership" />
<add name="MedVisitMembership" connectionString="Data Source="";Initial Catalog=aspnetdb;User ID="";Password=""" providerName="System.Data.SqlClient" />
</connectionStrings>
ask if you feeol any doubt in this.