Default Portal Language and Effect of the Application after change the Language

I am using the EP 7.0 and SAP ECC 6.0.

I have some qusetion regarding the Portal Languages.

1. How the Default Portal Language set in UME.Is it affect from the browser Language.

2. After change the Langauge in Portal how the ESS and MSS Application behaves.

Please provide any link or any SAP provide document for Portal Languages.

Thanks & Regards,

Sathesh