What does "Operation timed out after x with y bytes received" mean?

This error indicates that your web server failed to issue a complete response within the allowed time period.

If necessary, you can adjust the timeout period of your HTTP sensors.

Causes of this may include - but are not limited to:
- An overloaded web server
- Congested bandwidth resulting in slow transfers from your server
- A slow running web application
- Excessively large web page size

The error message also indicates how much data (in bytes) was transferred before the timeout period was reached.

A large number may indicate a lack of bandwidth - or a very large web page that couldn't be transferred in the allowed time.

A value of 0 may indicate a slow running or hung web application, which did not complete execution and hence failed to transmit any data at all.