Where do you suggest we go to find out more information about why a site is 503'ing? We'll get things like this several times a day:
2013-11-18 12:48:12.288 [INFO] [IP:56269-4#APVH_domain.com] connection to [/tmp/lshttpd/APVH_domain.com_Suphp.sock.078] on request #5, confirmed, 1, associated process: 354837, running: 0, error: Connection reset by peer!
2013-11-18 12:48:12.288 [NOTICE] [IP:56269-4#APVH_domain.com] POST request in process stage, fail with 503
2013-11-18 12:48:12.289 [NOTICE] [IP:56269-4#APVH_domain.com] oops! 503 Service Unavailable
2013-11-18 12:48:12.289 [NOTICE] [IP:56269-4#APVH_domain.com] Content len: 61676, Request line: 'POST /wp-admin/async-upload.php HTTP/1.1'
2013-11-18 12:48:12.288 [INFO] [IP:56269-4#APVH_domain.com] connection to [/tmp/lshttpd/APVH_domain.com_Suphp.sock.078] on request #5, confirmed, 1, associated process: 354837, running: 0, error: Connection reset by peer!
2013-11-18 12:48:12.288 [NOTICE] [IP:56269-4#APVH_domain.com] POST request in process stage, fail with 503
2013-11-18 12:48:12.289 [NOTICE] [IP:56269-4#APVH_domain.com] oops! 503 Service Unavailable
2013-11-18 12:48:12.289 [NOTICE] [IP:56269-4#APVH_domain.com] Content len: 61676, Request line: 'POST /wp-admin/async-upload.php HTTP/1.1'