it writes this error:

load: class K13.class not found.
java.lang.ClassNotFoundException: K13.class
    at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
    at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)
Exception: java.lang.ClassNotFoundException: K13.class

Does your sketch use OPENGL? exporting sketches that use it are usually... sketchy
Processing 2.0 is supposed to take care of this, but the alpha version doesn't even start on my computer.

Ive had the same error before, never found a solution.

well, the only other thing I can think of is that you aren't including the font files in with the applet... but that doesn't really make sense with that error. Someone smarter than me, come help! XD

At the page from the first link, I have instead the error: Exception in thread "Animation Thread" java.lang.RuntimeException: Could not load font DATA/Calibri-Bold-28.vlw. Make sure that the font has been copied to the data folder of your sketch.

The DATA name is strange, it should be lowercase 'data'.
Beside, if you generated the applet on Windows, there is a bug in 1.5 or 1.5.1 to access this folder from applets.

Was just about to say the same. I saw this in the java console...

http://www.czechdevelop.cz/nabytek/design_k/data/DATA/Calibri-Bold-28.vlw

Definitely something fishy going on with the fonts in the data directory.

Try exporting to an applet WITHOUT the fonts in the data directory and then afterwards copying the fonts to the data directory on the server. Make sure to use lower case. Your server is case-sensitive, which is also why your download link will not work, but lower case (L) l.zip does work.

The actual file on your server is

http://www.czechdevelop.cz/nabytek/design_k/data/calibri-bold-28.vlw

And again, this will only work with LOWER case.

So you might wanna change your processing code to:

1. fontP = loadFont("calibri-12.vlw");
2. font1 = loadFont("avantgarde-thin-12.vlw");
3. fontB = loadFont("calibri-bold-28.vlw");