WYSIWYG is an acronym for What You See Is What You Get.

It was introduced in the early 1980's to describe Desktop Publishing? programs where the layout on the graphical screen was a fair approximation of the printed version of the document.

The objective of browser-based tools that allow web page editing in WYSIWYG mode has been made difficult because of the great differences in the ways different browsers display HTML.

Reports and lists of WYSIWYG TTW (through-the-web) editors are available from

References:
Paul Browning's List
CMS Review