Uh, what? Offline how? Are you using XAMPP as a webserver for public access? Ie, from the Internet? Running it on a local machine, or something?
Of course you're running xampp on a local machine. What I'm asking is when is it "down"? Is this while trying to access it on the local machine? Or from external resources? Does it come up again by itself or do you have to restart it? Does it even run when it's" down", or are you talking about it not starting automatically when rebooting the computer?
Wow. Just... step away from the computer, or come back when you've learned to both read and write proper English. Seriously. "It's not working" is NOT ENOUGH INFORMATION. Hence why I asked a few questions, of which you've answered... zero.
Wait, what? Xampp is a program that makes it easy for web developers to create a local web server for testing purposes. If you're looking for something that could make your website be online, then you should purchase web hosting services.