I have a horrible horrible habit of skipping lines accidentally which sucks so bad! to help rid myself of this, I write the answer I chose in a big letter on the left side of the question so when it comes time to bubble, I leave no room for error.
Chrome is what I use, not a bad option. Are you sure you didn't accidentally hit the volume switch? If it's x'd out, it means it's muted. You can also try clearing your cache:
http://7sage.com/clear-cache/
I feel like there would be some serious complications with tablets. Some people might prefer to read on paper and I could see where you could accidentally click on the wrong answer
Mastermind. The 180 Watch does a few things better, but the Mastermind watch can't be broken by accidentally hitting the reset button while the watch is going.