CSSVista
CSS, Firefox, Internet Explorer, Tool, Windows April 28th, 2007
CSSVista is a free Windows application for web developers which lets you edit your CSS code live in both Internet Explorer and Firefox simultaneously.
If you like this, you may be interested in our browser compatibility service, SiteVista. Yes, that’s why this software is free! 
Features
* Live CSS editing
* Live rendering in Internet Explorer 6 and Firefox
* Split pane view to see both browsers simultaneously
* Completely free!
