Captchas. They're those "Enter the characters in the box below" tests that websites use to try and ensure that people registering are actually people and not robots. Apart from making life hell for the visually impaired, they tend to make life hell for the visually fine as well. In order to bypass Optical Character Recognition (OCR) software, the characters in the image file are usually distorted and have lines drawn through them to such an extent that it becomes more a matter of guessing than reading.
Admittedly, there have been some cool captcha systems, particularly the one which presents two scanned words from Project Gutenberg texts, the first of which is known to the computer and the second of which isn't. You enter both and the first is used to verify your (alleged) humanity while the second is sent off to the servers as an identified word. Sort of a massively slow and distributed OCR system.
But I have never before seen the system used by Shozu (if you can't work out what Shozu is for, don't worry - you don't need to know). First, you have to identify the symbols (not alphanumeric characters, symbols) and then you have to convert the symbols to alphanumerics using the key provided, and enter those characters.
I'm pretty sure that this is beyond the pale.