Solution : https://service.sap.com/sap/support/notes/895224 (SAP Service marketplace login required)
Key words : 
terms web dynpro portal integration reason, web dynpro application / iview, web dynpro application, relative page navigation, obn navigation step, portal navigation, netweaver portal, symptom usage, url parameter, session management
Related Notes : 
       
| 1283141 | Add. info.: Upgrade to SAP NetWeaver 7.0 EHP1 SR1 Java | 
| 1267573 | Central Note: Upgrade to Systems on SAP NW 7.0 EHP2 Java | 
| 1156186 | Add. info.: Upgrade to SAP NetWeaver 7.0 including EHP1 Java | 
| 1102065 | Add. info. on upgrading to SAP NetWeaver 7.0 SR3 Java | 
| 913972 | Add. info. on upgrading to SAP NW 7.0 SR1 Java |