Does every web designer always use CSS framework when building an interface?

Answer 1

CSS is critical for front-end design since it tells the browser how to display things on the page. Every thing from fonts to colors to object alignment is controlled by CSS.

Many designers will use CSS frameworks to speed up development, however you do not need to use one. In many cases it is easier to create a custom CSS file with only the styling you need rather than include an entire framework.