没啥自己的内容，推荐若干链接，这些是真爱，你值得拥有。

Principles of training multi-layer neural network using backpropagation

A Step by Step Backpropagation Example

Derivation: Derivatives for Common Neural Network Activation Functions

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NG的Tutorial

http://ufldl.stanford.edu/tutorial/

http://deeplearning.stanford.edu/wiki/index.php/UFLDL%E6%95%99%E7%A8%8B