CSS (Cascading Style Sheets) is a style sheet language that is used to control the appearance of web documents. One of the main uses of CSS is to ensure that web pages are displayed consistently across different browsers. Different web browsers, such as Google Chrome, Mozilla Firefox, and Internet Explorer, can render web pages differently due to differences in their rendering engines. This can lead to web pages looking different on different browsers, which can be frustrating for users.

By using CSS, web developers can specify how elements on a web page should be displayed, regardless of the browser being used. This helps to ensure that the page looks the same on all browsers, improving the user experience.

For example, a developer can use CSS to specify that all headings on a page should be displayed in a certain font and size, and that all links should be a certain color. This ensures that the page looks consistent across all browsers, even if the default styles for those elements differ between browsers.

CSS can also be used to create responsive designs, which automatically adjust the layout of a web page to fit different screen sizes and resolutions. This is important in today’s world where people access the internet from a wide range of devices, including laptops, tablets, and smartphones.

In summary, CSS is a valuable tool for web developers because it allows them to create consistent and responsive designs that work across different browsers and devices.