Thank you for your answer.
The URL is :
I think I am nearly done, here is a screen :
I would like to move the date just a bit more to the left side in the blue section instead of the red one.
Here is my CSS :
Atahualpa Theme options > Style POSTS & Pages > BYLINE BoxStyle:
margin: 10px 30px 10px 0;
font-family: Verdana, Geneva, sans-serif;
I probably have to modify "float: left;" by something else but I tried everything I found and it was not enough. :/