I changed my account's email address this morning and an email verification link was sent to that new email address. When I clicked on the link I was brought to a DSLR verification page, however the 'not a robot calculation' message box on that page was empty except for a small entry box and a click box to confirm 'I am not a robot.'
After playing around with it for a while I saw that I needed to highlight the message box to show what calculation had to be performed. I've never seen anything like that before so I'm letting you know in case this isn't by design.
I've attached two screenshots showing what the message box looked like before and after I highlighted it. If it matters, I'm on XP Pro SP3 with all updates; IE8 all updates.