Is that label printer supplied by or from UPS? If not and you're using one that you paid for, have you tried getting support from the manufacturer?

Can you do a Print Preview before you print a label?
File > Print Preview
Does the Preview show only one label? Or are you picking up two labels, or seeing more than just a label or two labels.

Thanks for the reply!! It is the printer supplied by UPS. I tried to do a print preview, but then it prints the label the wrong way.

I can confirm that this is happening in Firefox 3.0.19 with the UPS Thermal Printing Plug-in on one of our testing machines. It does not happen in IE 7 using the ActiveX control also supplied by UPS (in the same installation package), and it does not happen when I sent the file directly to the printer from the command line on a Linux box.

The label itself is written in EPL2, and looks correct (it looks like it should only be printing one label). All the browser really needs to do is send the contents of the file to the printer, but there's no native support for it in Firefox, which is why we need the plug-in.

If I had to guess, I'd say it looks like a problem with the plug-in itself. Windows (XP) complains that the print job didn't complete successfully when printing from Firefox, even though it printed fine. About 5-10 seconds later, the second label spits out. (Meaning that this problem could also be the OS trying to reprint the label after what it thinks is a failure.)

This also happens in Firefox 3.5.15 (on a different testing machine).

Sorry, I don't have access to a UPS thermal printer to be able to test that situation myself, but I am curious which preferences are set in Firefox for that printer.

There are two places where you can get that information, the first is Help > Troubleshooting Information - Copy All to Clipboard, then paste to a text program (not an option in 3.5.x versions and earlier versions, was new for Firefox 3.6). The other is through about:config and use printer as the Filter at the top.

I would suspect the printer plugin is sending the second command to Firefox, resulting in a 2nd label being printed - especially with that 5-10 second delay being there. My "gut feeling" that Firefox would spit the second page out a lot faster, if Firefox was causing that to happen.

Have you tried opening any of the files for that plugin to see if there are any plain Engilsh prefs that can be changed, or are those files all "machine language" like DLL's appear to be when opened in a text program?

IIRC, the UPS supplied terminal which contained a label printer that we had in the retail chain I worked for in 2000-2004 always printed two labels and we either tossed the 2nd label out or put it one another of the 6 sides of the box.