Cross-browser testing is essential for ensuring web application compatibility across various browsers and devices, focusing on functionality and design aspects. Given the multitude of browser versions, it is impractical to test every single one, so prioritization based on browser and device popularity is crucial. Utilizing tools like Google Analytics can help identify which configurations receive the most user traffic, thereby informing testing priorities. It is also important to test older browser versions, as many users, particularly in enterprise environments, do not update regularly. Audience demographics and consumption habits can guide educated guesses for testing focus, while recurrent support issues should be addressed promptly to enhance user experience.