Introduction of CSS/CSS3
Cascading Style Sheets is a style distance language used for describing the present of a document written in a markup language similar as HTML or XML. CSS is a foundation technology of the World Wide Web, alongside HTML and JavaScript. CSS describes how alphabet should be rendered on screen, on paper, in speech, or on other media. It's the utmost basic web designing language. It's easy to learn and apply. It's the language we use to term an HTML document. CSS describes how HTML fundamentals should be displayed. It allows one to adjust the present to different types of devices, similar as large screens, small screens, or printers. CSS is independent of HTML and can be used with any XML- based markup language.
What Mainly is CSS/CSS3

Why We Need CSS/CSS3
additional code means slower page speed. And CSS enables you to use lower code. CSS allows you to use one CSS rule and apply it to all circumstances of a certain label within an HTML document.However, it’s easy to do so with CSS, If you need to change the format of a specific set of runners. There’s no need to fix every individual page. Just edit the corresponding CSS stylesheet and you ’ll see changes applied to all the pages that are using that style distance. Responsive web design matters. In moment’s day and age, web pages must be completely visible and fluently passable on all devices. Whether mobile or tablet, desktop, or even smart television, CSS combines with HTML to make responsive design possible.