Understanding browser compatibility is essential for web developers and marketers alike, as more users access websites across a variety of devices and browsers. Key issues often arise due to differences in how browsers interpret HTML, CSS, and JavaScript. For instance, features such as Fetch API may work seamlessly in modern browsers, but could create problems in older versions. Furthermore, varied rendering engines can lead to inconsistency in layouts and designs, making it crucial to test your website across multiple platforms. Checking tools like Browse Happy can help identify compatibility issues with different browsers.

To tackle browser compatibility issues, a few practical solutions can be employed. First, employing a strategy known as graceful degradation involves designing for the latest browser versions while ensuring that basic functionality remains intact for older systems. Alternatively, progressive enhancement focuses on building a strong foundation that works for all browsers and adding advanced features for those that support them. Implementing feature detection tools can also guide developers in creating fallback options for unsupported features. Finally, using a responsive design framework like Bootstrap ensures that your site maintains functionality and aesthetic appeal across various devices and screen sizes.

Ensuring that your web application performs seamlessly across different browsers is crucial in today's digital landscape. This is where cross-browser compatibility testing tools come into play. These tools allow developers and QA professionals to identify and fix issues that may arise when users access a site on different browsers or devices. Below is a curated list of the top 10 tools for testing cross-browser compatibility that can help you deliver a flawless user experience:

1. BrowserStack - Offers real device cloud for accurate testing.
2. CrossBrowserTesting - Includes live testing, screenshots, and automated tests.
3. LambdaTest - Provides real-time browser testing with a range of integrations.
4. Sauce Labs - Focuses on automated testing across multiple browsers.
5. TestingBot - Facilitates manual and automated testing with a simple interface.
6. Browserling - Provides live interactive browser testing.
7. LambdaTest - Allows for testing across a variety of web browsers and operating systems.
8. MooTools - A well-known JavaScript framework that aids in cross-browser compatibility.
9. Can I Use - Offers browser support tables for HTML5, CSS3, SVG, and more.
10. TestComplete - An automated testing solution that supports multiple browsers.

There are several reasons why your website may appear different across various browsers. Firstly, each web browser has its own rendering engine, which interprets HTML and CSS code in distinct ways. This means that some styles or layouts you used might be supported in one browser but not in another, leading to discrepancies in appearance. For more information on how browsers render websites, you can check out Smashing Magazine.

Moreover, web browsers frequently update their versions, and these updates can affect how graphical elements are displayed on your website. Keep in mind that outdated browsers might not support the latest CSS features, which can result in display issues. It is crucial to test your website on multiple browsers and devices to ensure a consistent user experience. You can find some useful testing tools at CrossBrowserTesting.