Thank you for your reply.
I’ve seen in the screen images shawn on the presentation of the verb lite theme many examples showing an image at the top of the page, spanning the whole width.
I think this is the logo image. It takes the place of the title when you define it.
Whatever is the image size that I choose for the logo, my image is cropped to a small size (360×36). This is the size displayed by the Firefox developper tool, but I can’t figure out where (in which CSS or php file) this is defined. I have seen in the source of the page that there where a SRCSET tag, and maybe is it the reason, but is there a way to obtain a whole width logo?
Many thanks for your help.