polarity on unmarked capacitors
The only instance where polarity might matter is when using film caps (polystyrene or polypropelene) as bypass capacitors. In which case it's best practice to use the side with the outside foil towards ground.
I've seen a few audio circuits start to oscilate spontaniously at ultrasonic and even in the low RF range, although this would generally indicate poor circuit layout and other problems.
Film caps intended for this application generally have polarity marked. At any rate, 104 would be a .1uf capacitor which would in most cases be a ceramic disc or monolythic. Polarity is irelevant in these...