I will let others give a proper answer. It appears there have over recent months been quite a few posts about favicons, or bookmark icons not showing. I suspect there may well have been some sort of regression in a Firefox update that causes some of these problems.

I certainly get some unexpected blank squares myself, but it is a trivial annoyance, and I do not see a pattern to it. I have not yet taken the time to test this theory by creating new profiles and testing in safemode. (Or rather, I have not looked into this problem whilst in such modes)

Maybe you can give more information about your own problem, when does this happen, maybe attach a screenshot, and what sites are affected. It would be particularly interesting if you see this on any mozilla sites, so blogs, kb articles this forum etc.

Update:
I added a quick uncropped screenshot

• specifically selected tabs with no icons, normally they mostly show up
• screenshot is a new profile, safemode, Ubuntu Gnome desktop, Firefox 9
• I expect to see similar in firefox 7, 8, 10, 11on Windows7 & XP

I am unlikely to be able to comment further for a few hours, other things to do.

Type about:config in the Location (address) bar and press the "Enter" key. When you see a warning, click I'll be careful, I promise! button.

• Preferences that have been modified are shown as bold (user set).
• Preferences can be Reset to the default or changed via the right-click context menu.

-> In the Filter bar, type image.mem.decodeondraw

• Double-click the preference image.mem.decodeondraw to change its value to False
• OR right-click the preference image.mem.decodeondraw and click Toggle to change its value to False

-> Close the about:config tab and Restart Firefox.

Check and tell if its working.

I don't think FF10 is supposed to fix this "favicons" problem. For those sites that have icons in FF 9.0.1, they should remain in FF 10. At least that's my case. I am also using XP SP3 and FF 10.

Here is a screenshot with a circle showing some missing icons. Bookmarks do this too. For what its worth I have discovered that if I go to a bookmark with a missing icon then leave that address when I select the bookmark again the icon is there. Hope that helps a programmer. mah007 thanks for the tip. I have tried that to and it didn't work for me. Also thank you to John99 and silkphoenix.

This is a known issue (Bug 701297 - Several favicons are lost in bookmarks with the upgrade to Firefox 8).

Related discussion:

• /questions/893818 after updating to Firefox 8, I lost almost all the icons associated with my bookmarks. Bookmarks will work, but they show an empty square instead of the icon associated with the website they are linked to. What's the bug here??

Try using these extensions to restore missing Favicons:

-> CheckPlaces 2.6.1

• https://addons.mozilla.org/en-US/firefox/addon/checkplaces/

-> Bookmark Favicon Changer 1.59

• https://addons.mozilla.org/en-US/firefox/addon/bookmark-favicon-changer/

Check and tell if its working.

Alice, thanks for the note about the bug.

I will read it later maybe over the weekend, scanning through the bug it drifts over a few related subjects, comment 26 is highlighted as a summary but I am not sure that is up-to-date comment (if it is it may indicate an intention to close the bug) 75 is pointing out problems occur from previous releases and are not covered by the bug, no idea whether there are additional bugs for any such issues.

Meanwhile I attach another screen shot this time Firefox Aurora 11.0a2 on Win7 this one is not in safe mode, the only extension is Feedback 1.1.2 and plugins are Acrobat, Flash, Silverlight & Windows photo gallery.

I tried the two links offered by mha007. It helped with a few of them, but a significant amount remain. Thanks for the help.

Does it help to delete or move all places.sqlite files and try to restore them another time with the CheckPlaces extension?

If favicons aren't restore then that sounds like a problem with some of the tables in the places.sqlite database.
I don't know if there is any conversion code run to update SQLite databases when Firefox updates.
That has happened in the past and is one one the main reasons to never downgrade a profile.

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

• CheckPlaces: https://addons.mozilla.org/firefox/addon/checkplaces/