A 10 uF cap presents a 16 ohm impedance to GND to a 1 kHz frequency .
The same cap present a 16 kohm impedance to GND to a 1 Hz frequency.
A 10 uH rod inductor presents a 0.0628 ohm series impedance to a 1 kHz frequency .
If the cap is after the inductor it would pass through the inductor then through the cap to ground.
thank you for your replies, yes you are right, i was checking the app notes, i did not know there is application note too, so thank you for sharing CrossRoads
about the datasheet i have, it doesn't contains 24, it has 10.6, 26 pages
See the schematic at the TOP of page 145 on this DATASHEET
SEE the 10uH inductor and 100nf (0.1 uF ) capacitor connected to the AVCC pin ?
raschemmel:
See the schematic at the TOP of page 145 on this DATASHEETSEE the 10uH inductor and 100nf (0.1 uF ) capacitor connected to the AVCC pin ?
oops ok so i had a little part of it :o thanks for sharing raschemmel 
the datasheet covers everything related to the IC !!! wow !!! i checked the 24 section about ADC
no i do not see any schematic on the page 145, the section 18.6 
Page 245, NOT 145. ( that was a typo)
raschemmel:
Page 245, NOT 145. ( that was a typo)
oh ok yes i see it the cap and the 10uH conductor
oh ok yes i see it the cap and the 10uH conductor
THANK GOD !
Finally I can sleep.... ;D