Other Web Browsers

Besides Internet Explorer and Firefox, many other web browsers are available, including Opera (www.opera.com) and Safari (www.apple.com/safari). All these browsers differ in functionality, performance and features. Also, they employ different HTML layout en- gines, which determine how a web page displays in a browser. Firefox 2 uses Gecko as its layout engine, Safari uses a modified version of the KHTML layout engine and Opera and IE7 have their own engines. Gecko and KHTML are both free and open source.

Opera, as well as IE7 and FF2, is a browser designed to be accessible to all users, including those with visual or mobility impairments. Opera software also recently devel- oped a lightweight “Mini” version of the browser that runs effectively on mobile devices. Safari, originally created for Apple’s Mac OS, features an elegantly simple interface and impressive speed, especially when executing JavaScript (discussed in Chapters 6–11). Because browsers use different HTML layout engines, they may display the same web page differently. Additionally, some capabilities supported in one browser may not be sup- ported in another. The existence of different browser functionality and features makes cross-browser compatibility difficult to achieve.