The downtime just now was due to a DDoS.
I thought it was something to do with my connection. I thought it was just me who receives the 503 error earlier. How long has the downtime persisted? I tried to load bitcointalk for 15 solid minutes without anything, just 503 error.
I've been having troubles connecting to the site on and off for about an hour now, but it looks like everything is working fine now, so I'd say that the site was experiencing the DDOS attack during the last hour or so.