One of the favorite debugging tricks for HTML/CSS is using the CSS snippet you shared, known as the "Rainbow CSS" or "CSS Rainbow Debugging" technique. This technique applies different background colors to elements based on their depth in the DOM tree, making it easier to visualize the layout and identify any inconsistencies.

Another popular debugging technique is using browser developer tools extensively. These tools provide a wide range of features, including inspecting elements, modifying styles in real-time, debugging JavaScript, analyzing network activity, and more. By leveraging developer tools, developers can pinpoint issues in their code, test different styles, and optimize performance.

Additionally, utilizing CSS comments strategically can help in debugging CSS stylesheets. By adding comments to CSS rules, developers can provide context, document their code, and temporarily disable or test specific styles without removing them entirely.

Furthermore, creating custom CSS classes or attributes specifically for debugging purposes can streamline the debugging process. For example, adding a .debug class to elements or using data attributes (data-debug="true") can help target specific elements for debugging styles or behavior.

Lastly, logging messages to the browser console using JavaScript's console.log() function can be invaluable for debugging complex JavaScript interactions, tracking variable values, and identifying errors in code logic.

* { background-color: rgba(255,0,0,.2); }
* * { background-color: rgba(0,255,0,.2); }
* * * { background-color: rgba(0,0,255,.2); }
* * * * { background-color: rgba(255,0,255,.2); }
* * * * * { background-color: rgba(0,255,255,.2); }
* * * * * * { background-color: rgba(255,255,0,.2); }
* * * * * * * { background-color: rgba(255,0,0,.2); }
* * * * * * * * { background-color: rgba(0,255,0,.2); }
* * * * * * * * * { background-color: rgba(0,0,255,.2); }

By combining these debugging techniques and experimenting with different approaches, developers can efficiently troubleshoot HTML/CSS issues, improve code quality, and enhance the overall user experience of their web applications.

source - medium - Gajus Kuizinas