Form Problems

I just finished making a JavaScript quiz. It made the default answer "A" in the form so the user couldn't enter an undefined answer. Now, I am trying to make it so there is no default answer, and if the user doesn't answer the question, a pop-up window will appear informing the user that he/she didn't answer howevermany questions. The only problem is that I can't figure out how to test the form to see if one of the answers is undefined. I tried:
if (document.answers.elements[i] == ""), and
if (!document.answers.elements[i].checked), but those didn't work. Any help on this matter would be greatly appreciated.

Is "answers" the name of your form?

Try:

document.answers.elements[i].value == ""