If you check this website http://www.hackstavastergard.com/uthyrning.html you will then see that those 3 houres are background images and when I print them, then they aren't visible on the paper! What's only visible is the text and images of the food and the person who is sitting and writing its computer.
Any idéa how I can make it visible in print as well?

That's right, that's exactly how browsers print things.

Unless you tell them otherwise. You can't write it in the code, you have to tell your own personal browser to print the background image. Web pages aren't actually intended for printing, but for viewing on a PC. With a black and white printer, printing background images would mess up any printout, so excluding them is the default way browsers work.

That's right, that's exactly how browsers print things.

Unless you tell them otherwise. You can't write it in the code, you have to tell your own personal browser to print the background image. Web pages aren't actually intended for printing, but for viewing on a PC. With a black and white printer, printing background images would mess up any printout, so excluding them is the default way browsers work.

Oh I see.
So I was looking everywhere in firefox (ctrl+p) printing options and I can't find it anywhere. And when I go to the printing options for the printer I can't find anywhere saying "Print our background images too". :(

In firefox File > Page Set-up > Format & Options, tick Print Background