When you hit the “View Source” command in IE, it opens in a refreshing viewer. I mentioned viewer because you are not allowed to edit :).  Previous version used the notepad as an editor. If you still want to use the notepad as the default editor then press F12 to open developer tools Click File-> Customize Internet Explorer View Source –> select – Notepad. And one more thing to be mentioned – Developer tools Fantastic.

Here is the developer tool screenshot:

Check out the Menu Items to know what you can do with this handy tool bundled with IE8.

Cheers!