I have the problem that loading a certain webpage in firefox automatically opens the printer dialog. How is that?

Additional information:

• This only happens on firefox 24.0 on Windows 7. It neither happens on Windows Explorer in Windows 7 nor on Firefox 24 on a Linux system.
• This also happens when using the firefox safemode, with all add-ons disabled.
• I cannot post the webpage, since it is not public and restricted.
• Multiple javascript files are used, but none contains the expression print().
• The page content does not contain the phrase 'printer'. It has nothing to do with printing something.
• This happens sometimes, but not always. I cannot say for sure the URL and/or the content is always identical.
• I can answer any other questions, like 'Does the page contain this and that...', 'does the URL contain this and that...'

Basic question: What could be the reason for the annoying printer pop up?