CSSvista can be downloaded for CSS editing that can be debugged in IE and Fiffox at the same time_Experience exchange

For every Web developer, browser compatibility is a big issue, among which Firefox and IE are the most important user browsers. Generally, we will install different browsers for testing, and Firefox users can use the IE tab extension for debugging.
Now, you can try the following application, which may bring a lot of convenience to your development work. The interface is like Dreamweaer. The CSS code editing area is displayed on the left, and IE and Firefox are displayed in two columns on the right. The debugging effect below. Of course, the layout can definitely be adjusted.
This program can also be used to debug the display effect of your web page under IE and Firefox.

Tips: Only supports Windows XP and Vista operating systems. After downloading, you will get a Windows enhanced application download file in .msi format. But to run this application, you need to have .NET framework version 2.0.5.0215 installed in your computer. In addition, the website states that there is no guarantee that this program will work 100%.
Official download address