I am getting an 'Error 406' or a 'Bad Request'
This error means that the server has rejected your request because of its contents. The explanation for this is technical: some sequences of characters and commands are often used by hackers to exploit security problems in software. Therefore, our firewall inspects all page requests to check for possible hacks. This can be compared to a virus scanner. It could be that your post contains some "dangerous" characters. See if your post contains any weird characters or punctuation which could be the problem, and try submitting it again.
The most common reason for this is the use of brackets/parentheses. And the use of the word 'system'. And especially both together. Try copying your whole post to Notepad, and then pasting/submitting it a chunk at a time into Bluelight. That usually highlights the suspected terrorist part of your post. The easiest way to do this is to make a thread in Testing Grounds, then submitting it one paragraph at a time. Once you find the offending paragraph, you can then repeat the process by sentence, then single words, and so on until you find the offending characters.
Another reason you may be receiving this error could be due to the length of your post. If your post is particularly long, you may need to submit it in chunks. A post that copies into MS Word as 6 pages long, for example, will likely cause this error.