IE Tab, an extension from Taiwan, embeds Internet Explorer in a Mozilla/Firefox tab.
This extension is derived from the famous extension IE View, but much different. While IE View always open IE-only pages in a seperate Internet Explorer window, IE Tab can view them in a Mozilla/Firefox tab.
This is a great tool for web developers, since you can easily see how your web page displayed in IE with just one click and then switch back to Firefox. IE Tab is compatible with Firefox 3.