Merci Zet Man, tout est ok

Please stop spreading these kind of strange "advices", Gh0st Snipu.

If the location and the name of the image has not changed, there's absolutely no need for poking around in the code.

Changing the core files isn't recommended anyway - see https://www.opensource-socialnetwork.org/wiki/view/704/should-i-modify-core-files

system->plugins->default->pages->contents-> index.php and
change the "/" img src="<?php echo ossnthemeurl();?>images/logo.png" / to look like this
img src="<?php echo ossnthemeurl();?>/images/logo.png" /

then re-fresh your page. Worked for me just fine...all those olders topics/tutorials didnt work at all..this one works 4.4 version.

Please read the Ossn documentation first, before opening a topic.
Following the steps outlined in https://www.opensource-socialnetwork.org/wiki/view/1137/how-to-find-something-a-word-pattern-in-the-source-code you'll notice that the file you have to change is not logo.jpg but logo.png.