Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical web browsers developed by Microsoft and included in the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year. Later versions were available as free downloads, or in service packs, and included in the original equipment manufacturer (OEM) service releases of Windows 95 and later versions of Windows. The browser is discontinued, but still maintained. 

Internet Explorer was one of the most widely used web browsers, attaining a peak of about 95% usage share during 2002 and 2003. This came after Microsoft used bundling to win the first browser war against Netscape, which was the dominant browser in the 1990s. Its usage share has since declined with the launch of Firefox (2004) and Google Chrome (2008), and with the growing popularity of operating systems such as macOS, Linux, iOS and Android that do not run Internet Explorer. Estimates for Internet Explorer's overall market share range from 3.91% to 16.84% or by StatCounter's numbers ranked 3rd, just after Firefox (or even as low as 5th when counting all platforms), (browser market share is notoriously difficult to calculate). Microsoft spent over per year on Internet Explorer in the late 1990s, with over 1,000 people working on it by 1999.
When was Netscape the most popular browser?
Netscape, which was the dominant browser in the 1990s.