If you 'drag' a tab out of the current window, it open in a new window. Could this be the problem? ----------------- Security Issue: Update your Flash Player '''Note: Windows users''' should download the '''active_x''' for ''Internet Explorer.'' '''and''' the '''plugin''' for ''Plugin-based browsers'' (like Firefox). '''Note: Windows 8 and Windows 10''' have built-in flash players and Adobe will cause a conflict. Install the '''plugin only.''' Not the '''active_x.''' Flash Player '''Version: 23.0.0.162''' Flash Player (Linux) '''Version 11.2.202.635''' https://get.adobe.com/flashplayer/ Direct link scans current system and browser '''Note: Other software''' is offered in the download. https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) '''Note: Other software''' is offered in the download. ------------- See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Maybe you're triggering '''tear-off tabs''' and inadvertently opening the new windows? Here's an extension that allows you to disable that feature. https://addons.mozilla.org/en-US/firefox/addon/bug489729-disable-detach-and-t/

Hi! I installed the add on you suggested. This seems to have fixed the problem. Thank you very much!