Hello, Which Firefox version are you using? In the most recent version, unvisited bookmarks show up as dotted lines forming a square. If you are running the current version and you want to remove it, follow these steps: Hello,

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
Note: This will cause you to lose any Extensions and some Preferences.

• Open websites will not be saved in Firefox versions lower than 25.

To Reset Firefox do the following:

For Firefox versions previous to 29.0:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

For Firefox 29.0 and above:

1. Click the menu button , click help and select Troubleshooting Information.

Now, a new tab containing your troubleshooting information should open.

1. At the top right corner of the page, you should see a button that says "Reset Firefox". Click on it.
2. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
3. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Thank you.

Try to let all favicons expire to see if that makes Firefox to store properly them once again.

You can open the Browser Console (Firefox/Tools > Web Developer) and paste the JavaScript code in the command line and press the Enter key to run the code to reset (expire) all favicons.

var fS = Components.classes["@mozilla.org/browser/favicon-service;1"]
         .getService(Components.interfaces.nsIFaviconService);
fS.expireAllFavicons();

• FavIcon Reloader: https://addons.mozilla.org/firefox/addon/faviconreloader/

Reset Firefox {web link} is a LAST RESORT ! !

Move your mouse to the top of the Firefox window, then right click. You will see a menu of the available toolbars. Select Customize. In the new window, look for the icon. When you find it, hold down the left button on it, and move it to the tools box. What is it called?

Sometimes the places.sqlite file gets corrupted and a random favicon gets being used as the default favicon. I've seen that on a few occasions myself (it usually showed the Firefox favicon). Resetting the favicons has always fixed this, but deleting a bookmark and recreating it has never worked. Maybe editing the places.sqlite file with the SQLite Manager extension could fix this without losing all favicons, but it is likely more effort to find what is wrong.

@Jackson1442 I reset Firefox (version 30 and it's been there since previous versions). It's still there after the reset. Also, it still kept all bookmarks and history; I thought it was going to be cleared.

@cor-el At first I tried that here, but it said Components.classes is undefined, but then I did the thing at about:blank and it worked. Thanks! The strange favicon is gone!

@FredMcD It's fixed now, but before it was I went to customize like you said and the strange favicon wasn't in the list of icons.

Thank you all for your suggestions.

You're welcome