The connection took longer than the specified threshold.
HTTP addresses can specify a threshold, which allows the request to timeout earlier than the default 15 seconds. With this failure, you might also recieve a HTTP Connect failure.
When the http address is checked by our servers, we wait the specified threshold for a response. If we do not detect a response, this error will be triggered.
Under normal circumstances, when an http hostname is requested (e.g. example.com typed into your browser), the request goes out to a DNS server and gets converted into an IP Address. If this request does not take longer than your specified threshold to receive a response, then this error will not be triggered.