hello, can you try to replicate this behaviour when you launch firefox in safe mode once? if not, maybe an addon (something to do with bookmarks?) is interfering here...

Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

You can check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

It did not replicate in safe mode. After a normal restart it didn't show up for a couple of hours and then while composing a new email message it showed again. I seem to have eliminated it by resetting Firefox but lost my Chrome application in doing so.

This can be caused by a broken Live Feed (RSS) bookmark item, so if it returns again the check your live feeds.

Cor-el, How do I do I check live feeds?

Live feed items show with a specific orange feed icon and have feed location and site location instead of the location that a regular bookmark has.

• http://newsrss.bbc.co.uk/rss/newsonline_world_edition/front_page/rss.xml#

• https://support.mozilla.org/kb/Live+Bookmarks