what is it -?
such solid lag
error 500 is the most comon error that message do not mean anything it only tell you that the server has stoped executing the file due to a error. check on your server directory if you have any error.log file the real reason will be writed inside that file if you have error report activated in php.ini
The screenshot he posted was audiojungle.net. So it was an error with Envato that he was concerned about. 
Yes, Envato sites error quite frequently if you browse regularly. Just accept it and wait patiently until it fixes, next time you see it. 