Hi
You should not really edit the file in /etc with TextEdit. Besides you should try and back up the file first anyway. What you should use is a Terminal editor such as nano or pico or vi etc. Launch Terminal and issue:
sudo cp /etc/hosts /etc/host.bak
When prompted key in the local admin accounts password. You won't see it being typed so don't worry. That makes a copy of the hosts file just in case you screw things up. Next issue:
sudo nano /etc/hosts
Navigate using the arrow keys to a place where you can make your changes. It will be the line following the entry that looks a bit like this:
fe80::1%lo0 localhost
Control+O will write any changes you made. You'll be prompted to confirm the change. Press the enter key to confirm. When the change has been made Control+X will exit the editor. Quit Terminal when you're done.
Why do you need to edit the hosts file anyway? The interface is more than capable of handling DNS lookups.
Tony