I installed the Print Preview add-on to my toolbar. When I click on this icon to preview a page before printing, the scale is set at 30%. If I try to change the scale size or want to switch from portrait to landscape, my page goes blank and if I try to exit this screen and go to my home page or another web site, I keep getting the blank page. I have to close Firefox and restart it in order to get a web page to come up. I have one computer with 2 user accounts--my account and my husband's account. If I use the Print Preview in my husband's account, it works fine. Mine was working fine until a few days ago when this problem started.