I believe that the hardware engineers, graduating from the beginning of the company, in the design of PCB, the old engineer will say to him, PCB walk line do not go right angle, the line must be short, the capacitor must be placed nearby, etc..

But in the beginning we may don't know why to do it, is by a few they experience for us is far from enough, oh, of course, if you do not pay attention to these details, future and made, may be scold them, "said how many times the capacitance must be nearby put, put away the effects and so on" often experience tells us that in fact the old engineer is only a part of the talent truly master the secret, we will also need not sad, see more data will soon be able to master.

Until it is scold several times after we go back and find relevant information, why design PCB capacitance to the nearest put it, and look at the data and can understand some, but online information is spurious, rarely find a full explanation. The following is my reprint of an article on the capacitance decoupling radius of the explanation, I believe you can see after the cattle X answer and to avoid the occurrence of similar problems.