I've just bought a new Arduino Uno and I've been trying some easy tricks with simple leds. I was doing the fade effect from the examples on different Pins just to see if they work, so I was just modifying the number of the Pin. They were all working except 13,12,8,6 and 4. I am not sure if it is from the leds or from my Arduino, but I would like to see what you think about this. Thank you !
Aliicide:
IThey were all working except 13,12,8,6 and 4.
Hi and welcome.
On Uno, only pins 3, 5, 6, 9, 10 & 11 can do fading. These pins are marked with a "~" next to the pin number.
The other pins can be made to do fading too with a special library, but the example sketch can only use the above pins.
Paul
Credit where credit is due.
Full marks for personal research. You went through a detailed repetitive process of practical research to discover what would otherwise have required you to read the instructions.
I'd give you a thumbs-up smiley if there was one here. 
Thanks for the instructions. I often skip the instructions just to find them out on my own. I really had no idea that the answer to my question was there.
Again, thank you!
Aliicide:
I often skip the instructions just to find them out on my own.
Fortunately, Arduinox operate at low voltages.