Well, within a list of variables, I initialized the var earlier such as:
var location = 'no';
Then I used it such as:
Where later it gets run in the function:
winprops = 'width='+w+', height='+h+', top='+wint+', left='+winl+', menubar='+menu+', scrollbars='+scroll+', toolbar='+tool+', location='+location+', resizable='+resize+''
I added the var, then tested it, and it didn't work in Fx. Then I commented it out and tested it, and the page showed up. I repeated this at least 4 times! which produced the SAME results each and every time, so I came to the conclusion that that was the ONLY possible answer to the problem.
url = 'myWindow.htm';
popUp = window.open(url, 'myWindowName', winprops);
Perhaps it could've been that it conflicted with something else, b/c I used the location property numerous times elsewhere in the .js file.