I guess they wanted to make sure that people had answered the question so required a ‘none’ option. If you selected this radio button it used some JavaScript to clear any of check boxes you’d previously selected.

One of the best bits of interface design advice I ever heard was from Jakob Nielsen. In his list of Top Ten Mistakes it is number eight.

“Consistency is one of the most powerful usability principles: when things always behave the same, users don’t have to worry about what will happen. Instead, they know what will happen based on earlier experience. Every time you release an apple over Sir Isaac Newton, it will drop on his head. That’s good.

The more users’ expectations prove right, the more they will feel in control of the system and the more they will like it. And the more the system breaks users’ expectations, the more they will feel insecure. Oops, maybe if I let go of this apple, it will turn into a tomato and jump a mile into the sky.”

It’s important that any application or website uses mental models that people are familiar with. In security you’re often asking a critical question, and that’s all you want the user to think about, not a newly invented or misapplied design metaphor.

¹Formerly the British Computer Society, it has recently become “bcs – The Chartered Institute for IT” and is no longer referred to as “The BCS”.