You need to have a domain to do this, unfortunately. For losers without a domain, I'm afraid you'll just have to use some Loser-Be-Gone. Make a new document in Notepad & put this code into it.
deny from *IPADDRESSHERE* Put the IP address of the person you're banning. Save that document as htaccess.txt. Now, FTP/upload this to your site. Right click on the document and rename it .htaccess (now it will disappear). That person is now IP banned - meaning, he/she/it can't view your site anymore.