I take you on
for more information.
This integration language did not exist at the beginning on the web.
Those of my generation and the elderly who experienced the beginning of the Internet era surfed on very sober pages.
You can go to openClassRoom
to see the difference or on the twin page of it without css here (well, depending on the time, html could put images).
In addition, this language allows responsive, that is to say the adaptation of the style of the pages: sizes of the texts and images depending on the size of the screen used. Sometimes you will not have access to the same data depending on whether you use a smartphone, a tablet or computer.
Css is for aesthetics.
I propose you this gallery images.