After membership authentication,no redirection to the original page occurs.Why?

hi,
I am sorry. I wrote a similar post. Maybe i didn't make myself clear so nobody gives me a reply. So I rewrote my question:
We have multiple web applications(in one machine), we want all those  web applications to be authenticated by a single login page, that is, after logging in, you can visit any page in all those web applications. The login page is placed in a dedicated web application called Membership. The following is the config of the Membership web app.
<connectionStrings>
    <add name="MyMembershipConnString" connectionString="server=.;database=aspnetdb;trusted_connection=true" providerName="System.Data.SqlClient"/>
  </connectionStrings>
 
<membership defaultProvider="MyMembershipProvider">
      <providers>
        <add name="MyMe ...