Research is what I do when I don't know what I'm doing.
So I've been reading these 3 threads + wiki... and trying to sum up.
http://forum.processing.org/topic/single-jar-for-java-web-start-deployment
http://forum.processing.org/topic/post-to-web-library-question
http://forum.processing.org/topic/web-hosting-for-java-applet
http://wiki.processing.org/w/Export_Info_and_Tips#Applet_Export

1: export applet
2. create an Upload.php file, example here: http://libraries.seltar.org/postToWeb/
      OR create a jnlp file, example here: http://www.local-guru.net/blog/2010/01/11/deploying-processing-apps-using-webstart
 
3: zip applet + php file OR jnlp  file and then change file.zip to file.jar< which doesnt work for me, just makes file.jar.zip>
4: upload .jar file (which I can't create)  to web server
5. have your custom.html in your web page some how point to that file...

Cheers
<headtodesk><loop>