The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Thomas Gring:
Use UpToHTTP to create and send HTTP requests to test HTTP services and see how servers respond.Set request method, URL, header fields and body. Send requests and inspect server responses including redirects and detailed views of cookies and body.Add your own custom methods and field names, set the timeout value, control redirect and cookie handling.Connect to services that require HTTP basic authentication and choose to cancel or continue HTTPS connections with invalid (e.g. self-signed) server certificates.Use requests groups to logically groups requests and use the same base URL for all requests in one group.Install the "Add Request" bookmarklet in Safari to add requests from within Safari for the current web page.