[JBiserkov]

Well, Visual Studio 6.0's Visual Interdev (1998) had actual browser rendering (via the Trident engine used in Internet Explorer I assume), including Java applets, which would run in the "Quick view" mode, but also amazingly in the Source [code] mode!

[the_mitsuhiko]

Mozilla Composer also existed and is the root of a lot of WSISWYG editors today because of the legacy it and others left in the HTML spec (content editable).