我明白啦，
得这样写：

server {
                        listen ip1:80 default;
                        listen ip2:80 default;
                        listen ip3:80 default;
                        server_name _;
                        return 500;
                }

listen *:80 default;
listen 80 default

都会造成:

2011/05/12 16:55:56 [emerg] 635#0: still could not bind()
2011/05/12 17:18:33 [emerg] 635#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2011/05/12 17:18:33 [emerg] 635#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2011/05/12 17:18:33 [emerg] 635#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2011/05/12 17:18:33 [emerg] 635#0: bind() to 0.0.0.0:80 failed (98: Address already in use)
2011/05/12 17:18:33 [emerg] 635#0: bind() to 0.0.0.0:80 failed (98: Address already in use)

【 在 JulyClyde (信RFC1149得自由) 的大作中提到: 】
: errorlog开到debug级别看看
--
FROM 211.99.222.*