You can't break pennies.

Imagine you and your roommate have decided to go halfsies on groceries. Let's say the total comes to $16. How do you split the bill?

What if the total is $16.01?

Pixels are like pennies.

This vintage blog post explains how different browsers of the era handle floats and sub pixels: http://ejohn.org/blog/sub-pixel-problems-in-css/.

Do yourself a favor: avoid prime numbers.

Props to oksushi on the #css freenode channel.

oksushi: not sure you should bother about IE7 any more, but this article was interesting on the topic http://ejohn.org/blog/sub-pixel-problems-in-css/