What you are pointing at are folders.

Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences<Enter> in the address bar

Select Advanced > General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

Thanks for the reply.

Turned off "Use Hardware Acceleration", checked some websites, no problems to report.

Lines still appear in the bookmark sidebar.

Yes, I understand the screenshot shows folders, but the lines appear when the folders are expanded to show bookmarks as well.

Ahh now i understand. Those lines are separators that are in the bookmarks folder. Open the Main Bookmarks Folder <Shift><Control> B

I have the same thing. These are useful to separate groups. If you want to add or remove any, use the right click.

I'm aware of separators, and often use them to organize my bookmarks.

These are lines that appear when you hover over bookmarks in the bookmark sidebar. I posted a screen capture illustrating what I'm referring.

It looks like you're using an Apple PC, you might not be experiencing this same issue. I'm on a Windows 7 PC.

When you see the Gif, you'll notice I'm using a Stylish theme, though the lines still appear even with the default Firefox theme.

http://i.imgur.com/D28hQRG.gif

I love a good movie, where's the popcorn?

Now I see it. Can't tell with a still picture. I think its just the redrawing. Switch to the default theme and see if it still happens.

See:

• https://developer.mozilla.org/Mozilla/Tech/XUL/Tutorial/Styling_a_Tree