I would like to create a web page where there the background needs to say the same during the entire scroll. So, the real content of the webpage would feel like floating over the background.
Sorry I don't have any examples, but it would be like what Apple does sometimes when presenting their iPhone chip : for some time the page stays with the same electronic-circuit backgnd but chip specs like its speed keep appearing and scrolling
You can simply use:
body {
background-image: url("...");
background-size: cover;
background-repeat: no-repeat;
background-attachment: fixed; /* This is what makes the background seem to be staying in the same position */
}
However, if the background is very large, it may cause the scrolling effect to be slower.