IE6

Internet Explorer 6, commonly abbreviated IE6, is a web browser developed by Microsoft. It was released on August 24, 2001, and was shipped with Windows XP and Windows Server 2003. It remained the default Windows browser for many years, long after newer versions were released, contributing to widespread adoption and the dominance of the browser in the early 2000s.

IE6 offered improvements over its predecessor in areas such as JavaScript performance and security features, but it was criticized for poor standards compliance. It supported many CSS 1 features and partial CSS 2.1, yet it lacked full support for modern web standards, leading to rendering inconsistencies and reliance on quirks mode and vendor-specific hacks. The browser had notable issues with PNG transparency and the box model, among other quirks. It also faced ongoing security vulnerabilities and required regular patches.

Impact and decline: At its peak, IE6 held a dominant share due to bundling with Windows, shaping web development practices and browser compatibility testing. From the mid-2000s onward, competing browsers began to erode IE6's market share, and Microsoft released IE7 (2006) and IE8 (2009) with improved standards support and security. Support for IE6 effectively ended as part of Windows XP's end of life in 2014, with Microsoft advising users to upgrade.

Legacy: IE6 is often cited in web development as an example of how OS-level bundling can influence browser adoption and the challenges of maintaining legacy web compatibility. Its legacy includes a long tail of site-specific hacks and the broader push toward modern, standards-compliant browsers.