Meet Bespin – Web-based Framework For Code Editing
Saturday, February 28th, 2009
Bespin is a Mozilla Labs web application that is extensible web-based framework for code editing that aims to increase developer productivity, enable compelling user experiences, and promote the use of open standards via your browser.
They have a working experimental prototype, that demonstrates some of the concepts of Bespin and the possibilities that it opens up. It supports basic editing features, such as syntax highlighting, large file sizes, undo/redo, previewing files in the browser, importing/exporting projects, etc.

