Preliminary Web Server Set Up
JNLP is about launching Java applications over the Web, like clicking on a link in a normal HTML page shown in a browser. But in order to do this trick, you need to set some little details on our Web server. Contact your Web admin in order to know whether these operations were already carried out.
Essentially, the Web server recognizes JNLP files by means of their special MIME type. So, if not already present, you need to add the JNLP MIME type application/x-java-jnlp-file associated with .jnlp files.
Under the Apache Web server, for example, check the types file in the conf directory.