They are still down, but a traceroute to them reports they are using Prolexic DDoS filtering, so it must be something wrong with their server.
Code:
Tracing route to 21sexturycash.com [72.52.1.14]
over a maximum of 30 hops:
[SNIP]
11 38 ms 37 ms 38 ms 1-2.r1.lo.hwng.net [195.66.224.227]
12 55 ms 37 ms 36 ms unknown.hwng.net [69.16.189.66]
13 * * * Request timed out.
14 37 ms 37 ms 41 ms unknown.prolexic.com [209.200.156.50]
15 181 ms 181 ms 179 ms unknown.prolexic.com [209.200.176.226]
16 177 ms 179 ms 177 ms 72.52.1.14
Trace complete.