Introduction

Any client system (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with your Web server:

• Obtain an IP address from the IP name of your site (your site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
• Open an IP socket connection to that IP address.
• Write an HTTP data stream through that socket.
• Receive an HTTP data stream back from your Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

This error occurs in the final step above if our CheckUpDown robot receives an HTTP status code that it simply does not recognise.

Reasons for 003 errors

Your Web server may return a data stream that is incorrect in terms of the HTTP protocol. The status code it returns may be invalid (one not defined in the HTTP protocol) or the HTTP data stream may be fundamentally corrupt. The HTTP protocol is very clearly defined, so it is highly likely that this kind of error is defective programming by the developers of your HTTP server software.

Similar defective programming may exist in our software. The data stream your Web server sends may be correct, but we fail to parse it correctly. This could be a pervasive bug in our software, or one linked only to particular versions of the HTTP protocol.

Resolving 003 errors

There is nothing you as a user can do to resolve 003 errors you see on your CheckUpDown account. They are entirely due to differences in the interpretation of the HTTP protocol between our software and your Web server software.

Please contact us directly (email preferred) whenever you encounter 003 errors. Only we can resolve them for you. Unfortunately this may take some time, because we have to analyse the underlying HTTP data streams and may have to liaise with the vendor of your Web server software to agree whose programming is defective - ours or theirs.