If you entered a correct domain name (for example: microsoft.com or mozilla.org), this error means the domain is free, You can purchase it if you want to, Otherwise this error tells that the domain name you entered is malformed.
IP Whois: Essential information about your IP address.
Domain Whois: Important information about any existing domain with any suffix.
DNS Lookup: The ultimate DNS lookup tool, retrieve any domain's DNS records.
Ping: Check any server to see if it responds to ping requests.
Head Info: Retrieve the head infrmation from any webpage.
Test Port: Test for open ports on your side.
Trace Route: Run a trace route to see the path to a server.