Browser engines are crucial in determining how websites are displayed across different browsers, which can lead to cross-browser compatibility issues. These engines interpret HTML, CSS, and JavaScript, rendering web pages uniquely depending on the browser being used. Over time, browser engines have evolved from handling everything to being supported by specialized rendering and JavaScript engines, each contributing to the visual and interactive elements of web pages. Major browser engines include WebKit for Safari, Gecko for Firefox, and Blink for Chrome and Opera, each influencing how content is visualized. The historical development of browser engines began with Netscape and Microsoft's competition, leading to the introduction of JavaScript and the separation into rendering and JavaScript engines. Despite the dominance of Blink, diversity in browser engines is seen as beneficial for innovation, although it poses challenges for web developers who must ensure cross-browser compatibility. Cross-browser testing becomes essential to address discrepancies in how web elements, such as CSS properties, are interpreted by different engines, ensuring a seamless user experience across all browsers.