clipped from: www.labnol.org 
a. Carry a portable version of your favorite web browser on the USB drive? It could be Internet Explorer, Firefox, Google Chrome, Apple Safari or even Opera.
b. Simultaneously run multiple versions of Internet Explorer or Firefox on the same computer side-by-side without any hacks.
c. Test the new design of your website in all popular browsers without having to rely on an online service like Browser Shots?
d. You don’t have permissions to install new software on the office computer? How do you then use Safari or Google Chrome instead of Internet Explorer?
Now if you said yes to any of the above questions, all you need is Xenocode - it’s an awesome platform that helps you run any web browser on your computer without installation. Simply download an executable from the Xenocode website and double-click to run that web browser.