It works. Thank you Ciarán. For the sake of the members of the forum I tell you what I did next. As a consequence of adding a background image, I needed the top and the bottom modules be transparent to have the image visible through them. Following the logic of the code you gave me, I adjusted the last line to read:
body, #body_panel,
#container_top1_modules .wrapper960,
#container_bottom3_modules .wrapper960 {
background-color: transparent;
}
I don’t want to abuse your patience and time but I still have a problem with that background image.
To test what image resolution I should use I got an image I used successfully as a background in another project with the J51_Creative template (
http://www.work-ais.enasa.aero)
My PC screen horizontal resolution is 1920px
J51_Creative template size: 1120px
The horizontal resolution of the background image: 1400px
The image shows complete in the screen.
The same image in the same PC in Hannah template:
J51_Hannah template size 1200px (
http://www.agrupamento-alfredodasilva-sintra.pt/work) only in the main page submenus.
As I mentioned, the image horizontal resolution is 1400px
The image covers only part of the screen coming from the left and repeats.
If I add no-repeat to the code (background-repeat: no-repeat

the image does not repeat and the screen is blank to the right.
What shall I do to adjust the Hannah defaults?
Best ragards
wallis