CSS is used to design websites in addition to HTML
CSS is an abbreviation for ‘Cascading Style Sheets’. Style sheets format the HTML elements of a website, and determine how content or areas should be represented. With CSS definitions, fonts are formatted, background colours and images are assigned, elements are positioned and much more.
Style sheets are intended to complement HTML and were standardised by the internet panel W3C, the World Wide Web Consortium. CSS design is a web standard, in addition to various other technologies.
A big advantage of CSS is that form and content can be separated with CSS. The page content is structured with HTML elements, and the appearance of the elements is defined centrally in an external CSS file. This means that HTML creates the structure, and CSS takes care of the optical elements.
CSS 2.1 was the predecessor of CSS3 as style sheet standard
The internet is subject to constant change: CSS 2.1 was the standard for style sheets for a long type, and now CSS3 has now almost replaced it. Currently, there is a transition period taking place.
CSS offers many advantages: CSS has more possibilities than just pure HTML. CSS opens up completely new opportunities and allows sophisticated website layouts. Complicated tables and transparent GIFs are no longer necessary, the website source code is more streamlined and it is easy to develop complex websites. If style sheets are recorded in an extra file, then the effort needed to make changes to design will significantly decrease, since the work will be confined to an external style sheet. The changes in the main CSS file can also be adopted by all documents. Maintenance costs for content updates on individual HTML pages will also reduce, since clear code can be edited easier and faster.
HTML files become smaller if they only consist of structural markup. In addition, the loading time will be reduced since the external style sheet will only need to be downloaded once and can then be cached in the browser. Different output media such as PCs, tablets or smartphones can be specifically addressed with different style sheets. This lets printouts on paper be very reader friendly with extra instructions on page layout and font, and incorporating elements.
CSS lets you implement uniform layouts for large projects, because the style properties that were once defined on a central sheet apply to all HTML files that relate to the style sheet. The corporate design will remain unchanged. A further advantage of CSS is that the structure language of HTML is not ‘diluted’ through layout and font size instructions. Instead, the page content is structured with logical elements such as headings, paragraphs, lists and so on. This produces more meaningful code: the content is integrated, logical relationships are created and meanings are marked. The elements are chosen according to their function and meaning, and not according to their appearance. This is possible because elements are overwritten with CSS. In addition, CSS websites are search engine friendly and user friendly.
You can find more information on CSS on Wikipedia: https://en.wikipedia.org/wiki/Cascading_Style_Sheets and on the manufacturer’s official website: https://www.w3.org/Style/CSS/