User CSS is a Chrome extension developed by Dimox that allows users to easily add custom CSS to any web page. With this extension, you can quickly insert your own CSS code and see the changes immediately.

Using User CSS is straightforward. Simply press the extension button to display the CSS editor. From there, you can write your custom CSS code to modify the appearance of the current web page. Once you're done, you can enjoy the result right away.

One of the standout features of User CSS is its integration with CodeMirror, which provides syntax highlighting for your CSS code. This makes it easier to spot any errors or typos in your code. Additionally, the extension supports the Emmet toolkit, allowing you to write CSS code more efficiently and quickly.

User CSS also includes a convenient button that shows a green indicator when the current web page has custom CSS applied. This makes it easy to see at a glance which pages have been customized.

Overall, User CSS is a useful tool for web developers and designers who want to experiment with customizing the appearance of web pages. Its simple interface and real-time preview make it a breeze to use.