I read that when you get your card,you have to format it in your camera before you take any pictures.
This resets its file allocation table (FAT)and insures that it is ready for your camera. Also you have to format the card again each time that you clear it.
This insures that the FAT is in best shape for future use
Is it true?Have you any info?

I'm not sure, but that may depend on what type of card you have. I have not had to do it with mine and they work fine.

My understanding is that formating the card for your particular camera will make it work faster. If you don't format it, it will still work, just not as fast. :) I think I have switched cards between cameras and haven't always formatted them first and I haven't noticed any difference.

It says how to do it in my book but I haven't done it?? It says what it does but not the purpose?

I just checked the manual for my camera and it says that if the card was used in another camera it may have to be formatted in this camera for it to work properly. It says that it will give an "unable to use card" message if that is the case.

My understanding is that formating the card for your particular camera will make it work faster
In the Canon 60D,i used a SanDisk ultra 512 and i had taken about 14000 photos.First everything was very fast,but at the last 3000-4000 photos
they were displayed on LCD slowly and maybe the camera was generally slowly but i haven't noticed it

if the card was used in another camera it may have to be formatted in this camera for it to work properly

I have 3 types of cards,1 sanDisk,1 SanDisk Ultra and 1 SanDisk Extreme III and i was asked to format only once,when i placed the Extreme III into card reader and there were into card,some photos of the D60 and some of the 20D.I have never formated the cards in the camera,i think i have to try.