I am creating Stack Overflow client application and have reach limit to request. So I decided to get the Key from my application, but got a little confused.

 1. When I requested the Key I provided application site.  What is purpose of this site ? Can it be just my home page, git account or a personal blog ? Or do I need to implement some functionality on this site ?
 2. I got a Client Id, Client Secret and Key.  If I understand correctly I need to use only key ?  In which cases do I need the Client Secret ?
 3. Do I need to do something after I get the Key to make it works ? I am using [Rubyoverflow library][1], but I got error message when I set my key ("Invalid key")


  [1]: http://stackapps.com/questions/559/rubyoverflow-0-5