The CSS Viewport Rule is a set of instructions that allows web developers to control the size and scaling of a website's viewport. It enables developers to create responsive websites that are optimized for different screen sizes and devices. The rule is used to set the width and height of the viewport
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Cascading Style Sheets (CSS) is a style sheet language used for specifying the presentation and styling of a document written in a markup language, such as HTML or XML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.