1. A method for single sign-on of a user on a client machine to one or more target applications on target application servers in a computer information-processing network, comprising: before accessing said target application server, accessing an access server from a browser on said client machine; entering into said browser user-specific access server logon credentials for logon and access to said access server and logging onto said access server; while logged onto said access server, selecting a link to a target application of said one or more target applications from a linkpage presented to said browser by said access server, user-specific target application logon credentials for said target application having been previously stored in a registration database; after said selecting said link, said access server presenting to said target application said stored user-specific target application logon credentials for logon and access to said target application in a form and according to a protocol recognizable by said target application and thereby logging into said target application on behalf of the user and establishing a target application session between said client machine and said target application; after logging onto said access server and after establishing said target application session, bypassing said access server; and wherein said client machine is linked to said access server by a network, both said client machine and said access server are linked to a single sign-on engine by said network and said single sign-on engine is linked to said target application servers by said network, said single sign-on engine including two or more single sign-on logon servlets, a single sign-on database module, two or more single sign-on application servlets, a single sign-on registration database, a single sign-on database and a single sign-on error program module.