LED Sign Fequently Asked Questions
August 11, 1996
These are some frequently asked questions about
LED Sign. I will continue to add new questions/answers as they
arise to the
FAQ at the new LED Sign home page. So, if you don't find the
answer to your question here, check the FAQ at the link above.
My time is devoted primarily to the
O'Reilly WebSite Web Server. I get an enormous amount of
email, and I read a dozen or so usenet newsgroups and mailing lists.
Bottom line is that I cannot provide technical support for this
package. I hope you can understand. Darrick has provided a reasonably
complete set of documentation files, to which I have added to make them
represent V3.1. Like Darrick, I will delete any email I receive asking
for technical support. If you have questions about how to set up an
applet, check the java site at http://www.javasoft.com/. If you have
other problems, I would suggest checking the usenet newsgroups
- I've installed LED Sign on my machine as the instructions have
specified, but when I load the page I get an "Applet LED can't
start: security violation:security.protocol:file" error. What
- Usually this is caused by loading the file locally with "file://..."
or selecting "open file" from the file menu on Netscape 2.x or early 3.x
betas. According to Darrick, you cannot run LED Sign locally with
these versions of Netscape.
I have tested LED Sign 3.0 with Netscape 3.0b7 and Internet Explorer
3.0B2, and it will work reading the scripts, probably (!) because
the new packaged format and directory structure has the scripts and
fonts in subdirectories below the classes. I no longer have old
Netscapes so maybe this will work with them as well. Let me know...
Commercial use of LED Sign
- I read in the COPYRIGHT that LED Sign is for non-profit use
only. Can I use it on my company homepage?
- Yes. You may use LEDSign on a commercial homepage. What the
"non-profit" part means is that you cannot sell LED Sign in any way.
LED Sign is freeware, and I (darrick Browne) retain all rights to it. It
is NOT public domain. This means you cannot sell it in an internet
software "bundle", sell it in any type of commercial distribution, or
sell it to clients. If you are a web page designer and do consulting,
you may charge your clients for the time it took you to set up LED Sign,
but you may not charge for LED Sign itself.
- When I load my page with LED Sign on it, I get a "error:
java.lang.ClassFormatError". What is wrong?
- Contact your web server administrator. The error is caused by
the web server not knowing what a ".class" file is serving to
the browser incorrectly. Some web servers have problems with
this, others do not.
Applet can't start: applet not initialized
- I downloaded the LED Sign kit and have it installed on my
machine. When I try to load the page in Netscape I get a
"Applet can't start: applet not initialized" error and the applet
does not run. How do I fix this?
- This problem can be caused by two situations:
- You are using
Netscape 2.x or early betas of Netscape 3.0. For these versions, you
need to load the page over a URL with "http://...". If you are loading
it localy with "file://..." you will get the initialization and security
- You need to make sure that all the file names and paths are
correct in the <applet> tag in the html page. If the applet
can't find the files that it needs it won't be able to run and
it will give the "init" error.
<param name="script" value="../scripts/Demo.led">
<param name="font" value="../fonts/default.font">
<param name="border" value="3">
<param name="bordercolor" value="100,130,130">
<param name="spacewidth" value="3">
<param name="wth" value="100">
<param name="ht" value="9">
<param name="ledsize" value="3">
This is the example tag that is found in LED.html in the
distribution. I used relative paths so that the docs would load the LED
sign sample even when the LED.html file was loaded ad a file (works with
Netscape 3.0b7 and later, Internet Explorer 3.0B2 and later). I know
this is confusing if you don't understand how the CLASSPATH and
CODEBASE features of Java work. Please see
This is a packaged applet.
The tags that are critical are codebase, code,
script, and font. These paths and files must be correct
including capitialization. Codebase is the path to where the
com directory created during installation
can be found. Code is the main bytecode
"executable" file. Code should always be
"com.dc3.applet.LEDSign.LED.class". Script is the LED script
that the sign will run. And font
is the font file that the sign will use to display the
If you are working on a Win95/NT system and your ZIP program
changes file name size (truncates to the MS-DOS 8.3) or
changes capitalization, find a 32-bit ZIP program such as
WinZip 6.0a (available at most NT/95 download sites), and
reinstall the package.
error: ClassNotFound Exception
Q: When I try to load the applet, I get a "ClassNotFound" error
in the status bar of Netscape. What is causing this?
A: The codebase path in the <applet> tag is incorrect.
Just correct the path to point to the directory where all the
.class files for LED Sign are located and it should run fine.