A blank tab is opened when I click on a link to a PDF file. When I close the PDF file, the blank tab is still there and I have to close that tab. This recently started happening in the past month. My version of Firefox is 51.0.1 (32-bit) and I'm running Windows 10 Pro. In other words, if I am open a webpage in the 1st tab that has links to 2 PDF files and I left-click on one of those files, a 2nd blank tab is opened and the PDF file is opened in Abobe (not in Firefox). I like that the PDF opens in Adobe and not in Firefox. In order to open the 2nd PDF on Tab 1, I have to go back to Tab 1 to click on the 2nd PDF. When I close the PDF files, I now have my original webpage pluse 2 blank tabs. I have to close the 2 blank tabs. I don't want the blank tabs to open. I used to click on the PDF link and the PDF file would open in Adobe outside of Firefox and this is the way I prefer. This does not occur if the webpage is on my local computer but only when the webpage is on the internet. Any help is appreciated.