From Wikpidia: Windows Internet Explorer (formerly Microsoft Internet Explorer; abbreviated to MSIE or, more commonly, IE), is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems starting in 1995. It has been the most widely used web browser since 1999, attaining a peak of about 95% usage share during 2002 and 2003 with IE5 and IE6.
That percentage share has since declined in the face of renewed competition from other web browsers – Mozilla Firefox most of all. Its usage share now sits at approximately 50% to 60% and is trending downward. Microsoft spent over $100 million a year on IE in the late 1990s, with over 1,000 people working on it by 1999.