if Offline redirect script

[Neo_Pt]

hi there,

well i need a script (javascript or another ... ) that redirect if server is offline.

something like i want to access

http://localhost

but the server is offline so he redirect me to

http://www.example.com

how can i "say" to my index.html at localhost to redirect to example.com if he is offline?

or

how can i "say" to my index.html at example.com to "stay cool dont do nothing because localhost is offline"?

Thanks for the help !