Thank you Kaspars for your answer.
Infact; I found a very interesting code in
http://www.yvoschaap.com/youtube.html
Then I write my code in the way that if you select the channel you will have the video thumbnails –(exactely like you used in this page’s code) — I gave the user channel as well ofcours.
Then if we choose a playlist we will have videos thumnails.
But each time i had to enter the playlist code .

“So” if we add a video in any of the playlists ; this will be added to our site , but if we add another playlist , we wont see it and we have to add it manually.

So i was interested to know if we can add only “user name’s channel” and then get the “playlists id” within the channel.