The script is designed to check which pages are responding to the request. Those which are active can be pressed.
What you need is fping. Ubuntu and similar:
sudo apt-get install fping
Download the script, open a terminal in the folder where you downloaded it and change the run permissions:
chmod +x check_sites.sh
The script is ready to run. Some systems allow you to run fprint without sudo others do not. Try this:
./check_sites.sh
If it doesn't work:
sudo ./check_sites.sh