I'm guessing he is using water slide decal paper.
I have some A4 sheets somewhere ... some are clear, some are white. You can print a logo (or any image) on it using a printer or photocopier; cut out your logo; immerse it in water; and the top very thin plastic sheet slides on to your headstock ... just like those temporary tattoos you could get as a kid.
In my experience you need to shoot A LOT of clear over them to get the edges to disappear. One trick is to cut as close to the edge of your logo as possible so it's less obvious.
i apologize again fro my bad english..that's what i mean....my problem is that when i put it in water,the colour went off.so i must seal it with a liquid....this liquid made a little mess in my logo..i mean that besides the black color,a red colour appeared....and by putting it the headstock,and shoot with sealer,it was obvious that it is a sticker...i am very dissaponted cose i cannot find a descent decal to my my work correct...really disapointed...i called back the shop i bought them and asked my money back!!!in the photos the result i see is very professional, ....i will look for vinyl decals as the guys here suggested me!! thanks again !!!