Firefox opens the home pages in a new window, so if you want to open a new window blank then you need to set the home page to about:blank

You can check the startup setting:
Tools > Options > General > Startup: "When Firefox Starts": "Show my home page" | "Show a blank page"

Ok, thanks very much. I discovered that my "home page" was not just a single page, but rather an entire configuration of some twelve tabs. Every time I opened a new Firefox window, all twelve tabs opened in it too. Also anytime I clicked the home page icon in the navigation toobar, all twelve tabs would open again...and again...

This started when I used the "Use current page" button in the General options pane to set a different home page. I didn't read the button carefully enough to see that it actually said "Use current pages".

I had never considered a "home page" to be anything but a single web page, certainly not a multi-tab configuration of pages. Seems to me this button could be more properly labeled as "Use current tabs configuration" or "Use all currently open pages" to make it more obvious that it is setting one's "home page" to a configuration of multiple tabs. Also, in the General options pane, the label "Home page:" could well be labeled "Home pages/tabs configuration:" or something along those lines to make it more noticeable that the "home page" is not necessarily a single page.

Thanks very much for the response.