Various web browsers

Browser	Release date	Platform	Rendering engine	Standards support
Microsoft Internet Explorer 6	2001	Windows, Linux, Unix	Trident IV	CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (with proprietary implementations and quirks)
Microsoft Internet Explorer 5 and 5.5 (Windows)	1999 (5), 2001 (5.5)	Windows, Linux, Unix	Trident II (5) and III (5.5)	Most CSS 1, some CSS 2 (with bugs), partial support of ECMAScript/DOM
Microsoft Internet Explorer 5 (Macintosh)	2000	Macintosh	Tasman	CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (buggy and not complete)
Netscape Navigator 7	2002	Windows, Macintosh, Linux, Unix	Gecko	CSS 1, most CSS 2, ECMAScript, DOM
Netscape Navigator 4	1997	Windows, Linux, Macintosh, Unix	N/A	Some basic CSS 1, JavaScript, no DOM because it was written after NN4's release
Firefox 1.0	2005 (pre 1.0 release versions available in 2004)	Windows, Linux, Macintosh, Unix	Gecko	CSS 1, most CSS 2, some CSS 3, ECMAScript, DOM
Opera 8.5	2005	Windows, Linux, Macintosh, Unix	Presto	CSS 1, most CSS 2, ECMAScript, DOM (Opera 7 was the first version with DOM support)
Safari	2002	Macintosh OS X	KHTML	most CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (with bugs)
America Online	Various	Windows (there is a Mac version, but it isn't as well supported)	Trident	CSS 1, some CSS 2, ECMAScript, DOM (same as Internet Explorer, but expect additional buggy behavior)
Lynx	1993	Unix, Windows, Macintosh	N/A	N/A

Rendering Engines

A rendering engine, also known as a layout engine, is the code that tells the browser how to display web content and available style information in the browser window. The rendering engine is responsible for the size of an unstyled h1 heading or how a horizontal rule looks on the page. It's also the key to the correct implementation of CSS and other web standards.

The first separate and reusable rendering engine was Gecko , released by the Mozilla developers in 1998. It was notable for its small size and excellent support for standards. Now web developers pay attention to underlying rendering engines as a key to understanding a browser's performance.

The Wikipedia, an online collaborative encyclopedia, has a detailed comparison of rendering engines, where they are used, and what they support at http://en.wikipedia.org/wiki/Comparison_of_layout_engines.