Question

When I scroll up or down, I want a box/div to move up or down too.

For example:

See categories box

Answer 1

in your css write
#my-box {
position: fixed;
}

it will probably move it from the center so you will have to do some math if it is a fixed width and height box like

   #my-box-fixed { 
                     position: fixed; 
                     width:200px; 
                     height: 150px; 
                     top: 50%; 
                     left: 50%; 
                     margin-left: -100px; // half of the width
                     margin-top: -75px; // half of the height
    }