To create this special effect, utilize the VW (Viewport Width) and VH (Viewport Height) CSS3 units within the style properties of the div element.
For example:
#landing-box {
width: 100vw;
height: 100vh;
}
One VW unit represents 1% of the viewport's width, while one VH unit corresponds to 1% of the viewport's height. By setting a div's width as 100vw and its height as 100vh, it will always occupy 100% of the viewport's width and height.
A common mistake is using percentage values for the width and height properties, which are relative to another element's size and not directly tied to the viewport dimensions.
The element you referenced on the website starts at the top and isn't fixed, creating the illusion of a scroll function. When you scroll, you move to the next element because the first one was perfectly sized to fit your viewport.
This setup also simplifies adding a scroll button like the one on that site, as you know the div will always be 100vh tall. Therefore, you can programmatically scroll by that amount with JavaScript.