The client offered on this page is built using javascript and either websockets or flash. It may not work on some (mostly older) browsers, such as Internet Explorer 7 and below.
If the client doesn't load, first try reloading the page. If it still doesn't work, you can try enabling javascript (as well as flash), or use a different browser. Alternatively, use the ZMud or Pueblo client, plain telnet, or download a more complete mud client elsewhere. To connect to hotl3 on another client (or telnet), just connect to hotl3.com on port 5000 (or 23).