I'm trying to use the Url Rewriter functionality in my developer edition account but can't seem to get it working.  I get an invalid class error message when creating my apex class (see below) and I also can't see the URL Rewriter field in the Site itself.  Is there something I need to do to get this working or is this not available yet?  I assumed it should be available now my developer edition account has been upgraded to Summer '10.

I'm using this code in my apex class:

global class yourClass implements Site.UrlRewriter {

    global PageReference mapRequestUrl(PageReference yourFriendlyUrl)
    {
    }
    
    global PageReference[] generateUrlFor(PageReference[] yourSalesforceUrls)
    {
    }
}

The error I get is:

Error: Compile Error: Invalid class: urlrewriter at line 1 column 35