I love favicons. It helps me associate sites easily with their icons. I don’t have to read through names and descriptions and that saves me a lot of time. But for those who’d rather have a neater bookmarks folder, this little tweak may be of service. You can disable favicons from displaying by doing the following.
- Access the about:config page.
- Find the
browser.chrome.site_iconspreference name - Double-click on it to change the boolean value to false
- Find the
browser.chrome.faviconpreference name - Double-click on it to change the boolean value to false
- Close the about:config page/tab
- The changes take effect instantly

Check this out: http://www.tomkeays.com/blog/archives/2007/01/24/004337.php
problem with this advise is that it only prevents new favicons from being added to the bookmarks, existing favicons will still remain in your bookmarks…..
>problem with this advise is that it only prevents >new favicons from being added to the bookmarks, >existing favicons will still remain in your >bookmarks…..
Remove places.sqlite from your firefox settings. Next time you start it, the file is regenerated without the favicons.