Hi arsondpi,
and thank you so much for your quick answer.
But i'm afraid that i am such a nut that i didn't succed.
Here is what i did:
Upload the gif in the "exhibit manager" (no eror message, everything seems to work properly)
Then I re-upload in filezilla ( i re-sent the file from the local part toward the server. Then it asks me if i wanted to replace it, i did it)
Back on indexhibit, i refreshed the page, but it still didn't work.
About the format:
I tried different options. witch one does not change the size?
-over and over
-Horizontal
-A "grow" or "overlay" picture (fullpx) from documenta format
If you understand where i mistaken myself, tell me.
Thank you and sorry for being that dumb ; )