many developer want to use many version of a application. Firefox have not facility to stand alone installation but here is a trick to enjoy their nightly and stable version both.

make a folder anywhere in your system. make two folder the name depend on your choice. in first install the Firefox Nightly and second install the current stable version 3.6.12

now the application already add to your start menu otherwise add them manually. now you can use both version nightly and stable.

if you deug your web application in IDE such as visual studio or other then they force to open the default browser set in your system they open the version who you use last time. if you use last time nightly then they open your web-application in nightly otherwise in current stable version.