Sometimes we want to define a vertical height of a page, based on a specific element.
It is quite simple to implement, using fixed values (not pixels), but it's more complicated when using relative heights (percentage).
This problem is often encountered when using background images to create a border with a certain style to an element.
To set a vertical height on an item, it is necessary that every parent element have a defined height too.
We must define a height tags to html, body, and all tags containing the element must have a certain height.
This gives for example: