Minify your CSS by removing all the unnecessary characters.
Minify your JS by removing all the unnecessary characters.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get all possible details about a domain name.
Get approximate IP details.
Get all possible details about an SSL certificate.
Make sure your passwords are good enough.
Check if the URL is banned and marked as safe/unsafe by Google.