How accurate must my CAPTCHA responses be?
You must complete a CAPTCHA accurately, with a few exceptions.
Captcha responses are case-insensitive.
We do allow alternative responses for specific characters when our testing suggests that those characters are often mistaken for other similar characters. We accept, for instance, both '8' and 'B' as a response for "B", and accept both 'O' and '0' as responses for 'O'.