Re: how can i unsubscribe all feeds at a time

Unfortunately, there's no easy way to unsubscribe from everything at once.

However, you can import an OPML file. Open the "Your Subscriptions"
drawer, and from the "More Actions..." menu select "Import
subscriptions".

To add a feed by its URL, use the "Add a feed" link from that page or
simply enter its URL in the "Search for new content" box.

Mihai Parparita
Google Reader Engineer