Where to find that connection string is used.

Dear all,
         I have folllowing text in web.config 

<connectionStrings>
  <remove name="LocalSqlServer"/>
  <add name="LocalSqlServer" connectionString="Data Source=henry;Initial Catalog=amadeus; uid=euser;password=epwd;"/>
  <add name="hkamadeus" connectionString="Data Source=henry;Initial Catalog=amadeus;Persist Security Info=True;uid=euser;password=epwd" providerName="System.Data.SqlClient"/>
</connectionStrings>
And I found the Asp.net Membership is using the "LocalSqlServer" connection string. But I cannot
find where it is used. If I change the password of "LocalSqlServer". The program immediately
reflect that the login fails. So how  can ...