How do I get rid of the annoying advertisement that shows for a few seconds when I open Firefox Portable?

That's called a splash screen. It's there for two reasons. First to make sure a user knows they've started the app when they've clicked on it and don't try to launch it again (mainly for users of slower flash drives where it can take 30 seconds to launch). And second to ensure users know that it's a packaged version of Firefox, so they don't go bothering Mozilla for bugs related to the portablization of it... they know to come to us. Mozilla Firefox, Portable Edition is a licensed version of Firefox so all kinds of things including the name of it and the exact layout of the splash screen were worked out and agreed upon with Mozilla.

To disable the splash, if you use the PortableApps.com Platform, you can just tick a box in the Advanced Options to disable all the splash screens in all our app launchers (Thunderbird, FileZilla, Notepad++, etc). Note that this won't disable splashes within the apps themselves. Some apps like GIMP and LibreOffice have their own internal splash screens.

If you don't use the PortableApps.com Platform, just copy the FirefoxPortable.ini file from the FirefoxPortable\Other\Source directory to the FirefoxPortable directory and edit the line that says DisableSplashScreen=false to be DisableSplashScreen=true. There are some other options in that file, too. They're explained in the readme.txt file in the Source directory.

If you're ever curious about options like this in other apps, just check out the included help.html files. For apps with advanced options in the launcher, there's a link to the readme.txt within the help.html file. And if you ever encounter anything within that you'd like to know more about, please feel free to ask in the forums or on our live chat you can find on our support page.