Hello, I was wondering how to do to put a background that fits with the screen.
I like code, I simply put background = "image.jpg"

thank you

There are a few ways to do this, like this (CSS):

body {
  background: transparent url('.../images/bg.jpg') no-repeat;
}

Check out w3schools for all of the properties and their options.

http://www.w3schools.com/css/css_background.asp

thank.