The short form of Cascading Style Sheet is CSS. The simplest way to determine the structure, size, shape, position, colour, mobility, etc. of different types of web pages is CSS.
Why CSS?
There was a time when only a web site was designed by HTML. At that time the design was meant to describe different font colours, sizes, different cell colours, full-page background colour, and necessary image additions on a web page.
For each element of every page, we had to set the colour, size differently. Which was a complex process, and time-consuming matter? Currently, if there are 1000 or more similar pages on a web site, the design is still complete using a single CSS script.