How do you access the page? With the applet viewer, with a browser, which browser...
I am asking this because of the NumberFormatException. Is it coming from the applet or from the browser/viewer?
I went to your URL with IE11/Java1.7.0_51 and all was ok up to the point where I got the applet security prompt, where I refused to let the applet run.
Thank you for your response. Well if I understand this correctly then the app runs in the browser window (I use Win 8.1, IE 11). To see the error message I click on the button area in the browser window. Confirm the security warning (publisher is correct and trustworthy). Then I see the error message where the app button should appear. Clicking that I see the described error message. Also see in the Java console "setSize queried" (that is all). Not sure I am very helpful here - that is about all I see and can describe.
After uploading to the web server I get an error message
NumberFormatException For input string: "i>>?<html>"
I don't see any mention of ANYTHING you have done to try to troubleshoot the problem.
You have a file that you think is causing a problem when it is uploaded - then the obvious thing to do is do NOT upload that particular file and see if you still have the problem. If the problem goes away it was that file that likely caused it.
Take steps to isolate the problem and identifying what is causing it. You have the code, we don't. You have the files, we don't.
Post details of the things you have tried yourself since you created this thread.
Look, your applet wants to load the file http://www.neusob.de/karlskron/gemeinde/bewerber.dat
This file does not exist on the web server. Follow the URL and you will see that the web server provides instead a HTML stream telling you that it cannot find the requested file.
Your code tries to parse this HTML and fails, because it attempts to decode a number (NumberFormatException!), where there is none.