Disable the start-up screen
PortableFirefox is a light version of Firefox, which can be used directly from USB flash drive without any need to install it.
http://portableapps.com/apps/internet/firefox_portable
Here's how to disable the startup screen PortableFirefox:
In the subdirectory Other\FirefoxPortableSource, search for a file named FirefoxPortable.ini
Copy this file into the same directory as FirefoxPortable.exe
Then take a text editor and edit this file:
Change: =
DisableSplashScreen=false to DisableSplashScreen=true