I'm not sure on the filtering system, but most filter the URL and/or IP. You could try using the integer which would be http://3485924070/. However, since RioCar.org is a virtual host (something I didn't know prior) the server is not set to respond to the integer (or even IP address). This could probably be resolved easily on the server side.
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-Rob Riccardelli
80GB 16MB MK2 090000736