Hello,

In order to better assist you with your issue please provide us with a screenshot. If you need help to create a screenshot, please see How do I create a screenshot of my problem?

Once you've done this, attach the saved screenshot file to your forum post by clicking the Browse... button below the Post your reply box. This will help us to visualize the problem.

Thanks!

Curtis

https://support.cdn.mozilla.net/media/uploads/images/2013-09-17-08-51-04-afc1f9.png

Hey Tom,

Could you please open the View menu, and then screenshot again with the View menu open? I think I have an idea what's happened.

Curtis

The left side page looks like in might be in the Sidebar. How did you load that page, from a bookmark? And if so, look at the Properties for that bookmark and see if Load this bookmark in the sidebar is check-marked. If so, un-check it.

Then repeat that for any other bookmarks that open in the sidebar. That check-mark can happen by using "Bookmark this Page" on a web page; the JavaScript the website uses is faulty. IOW, add new bookmarks using Firefox, not by using buttons on a webpage.

Prnt Scrn Doesn't work probably because I'm using an external monitor with my laptop. Can you give me a clue as to what you might be looking for in the VIEW menu? I have checked it out.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Problem solved!

I had an add-on called "tile tabs" enabled. I don't remember doing that but there it was. I removed it.

Thanks to all!

Tom