Creating a responsive grid in CSS involves the use of media queries and the CSS grid layout system.
Here is an example of how you can create a responsive grid layout:
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In this example, for screens larger than 600px wide, the grid will have 3 columns. For screens between 400px and 600px wide, the grid will have 2 columns. For screens smaller than 400px, the grid will have just 1 column.
This is responsive design, as the layout adapts to the size of the screen.
Remember that the order of media queries matters. The browser will use the first media query that it matches in the list, so you should place larger viewpoints below the smaller ones. This is because CSS prioritizes the rules that come last when several rules apply to the same element.