A help button with some info on the usage will be nice. This can be separated or if it's easier to start with, just summarized in a page. From registration and login to search. Every functionality should be explained, at least very briefly.

Some ideas:
- which OpenID work and which not.
- how to search for data. what information is stored (e.g. no file name!, only alphanumeric stuff)
- explain that you only need to access one gateway and that the data comes from the datanode directly. No benefit from downloading from many "gateways" at the same time as this is in fact not happening.
- explain replication in relation to this last point.