When I develop web-based applications or websites, I need to test browser compatibility to make sure that every browsers like IE, Firefox, Opera, Chrome, and Safari display the expected result.
I find that it is difficult to test across many browser because I have to open many browser or window at a time. Then, have to press [ALT + Tab] to switch between browser and [CTRL + R] to refresh it to see the result.
Now I'm looking for an easier and faster way to test my website, maybe there is a software that can contain many in one browsers, and you can switch them only by pressing a single click to what browser you want to use.
Its not interactive, but I found nothing as fast and reliable as the BrowserLab from Adobe.
https://browserlab.adobe.com/
The best feature is the onion-skinning support, with auto align (type A).
Lunascape is a browser that allows you to switch between Trident, Webkit and Gecko; so it may be of some use for testing how a page will render in different browsers. I use it extensively, though I also test in all the main browsers (at various versions) as well.
Microsoft Expression SuperPreview. Alas, it is not free!