Trident (also known as MSHTML) is a proprietary layout engine for the Microsoft Windows version of Internet Explorer, developed by Microsoft.It was first introduced with the release of Internet Explorer version 4.0 in October 1997; it has been steadily upgraded and remains in use today. For versions 7 and 8 of Internet Explorer, Microsoft made significant changes to the Trident layout engine to improve compliance with web standards and add support for new technologies.