Hi,
What happen to your "shopping cart" ?
I can't see it. Since the "shopping cart" page does't exist, AJAX loading doesn't work, so does the "dropdown shopping cart" doesn't work.
The non-sef URL of "shopping cart" has this URL:
www.jouets-de-france.com/index.php?option=com_virtuemart&view=cart
But this URL goes to your homepage, furthermore... look at the screenshot:
Attachment Pasted_Image_1_9_13_11_55_PM.gif not found
Once you solve this "hidden shopping cart" page issue, the "dropdown shopping cart" will also start working..
Regards.