That can be caused by having some bookmarks with a long title.
The width of a column in the Bookmarks menu list is in current Firefox versions automatically adjusted to fit the bookmark with the longest name.
You can check the names of the bookmarks and make the longer ones shorter.

Are there plans to change this?

Adjusting the width of bookmarks to narrow them is not a viable option. It would be easier to change programs than to go through many layers of bookmarks

This is a continuation from: http://support.mozilla.com/en-US/questions/806255

You only need to change the long titles in the main Bookmarks Menu folder.

Continuing along, it seems that the way some of us prefer it (short width) is most likely in the minority, but the pulldown window is discerning for those who do not wish to see all that white-space prior to scrolling down.

It appears that Firefox takes the name of the bookmark it creates from each website's title page. (eg: Craigslist).

A better option option to changing long names to shorter ones would be to offer an option of a "bookmark or pulldown window width". I would be able to change the width to suite me and it would apply to all of the windows.

Thanks for the tip about checking the length of saved page titles After truncating excessively long names, my Favorites bar is now back to a normal. size.

I have had this problem with every version after FF4. The words in all drop down menus are spaced really far apart making the drop down box as wide as the monitor screen. I have not attempted to try a newer version for months until today, after we got another laptop and FF9 worked fine on it using the same display settings in Win7 personalize (medium). So today I tried FF9 and once again had the same issue until I changed my Win7 personalize display settings to the smallest option. With that option it looks normal BUT everything else is too small!!!! Is there no reasonable fix for this? BTW, before I upgraded to FF8 I first cleaned the FF4 out completely including the folder in documents/settings and saved the bookmarks to a flash drive, ran a registry cleaner and made sure FF4 was gone, settings were gone, etc. A clean install. There were no bookmarks at all to cause the issue.

This thread is about a problem with the Bookmarks menu on Mac.
You seem to have a problem with all menus on a different platform (Windows 7), os it is better to create a new thread for your problem.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Sorry I didn't catch that it was a mac forum... I guess you missed the part where I said it was a fresh CLEAN install of FF, all untouched even by imported settings and bookmarks. Thanks anyway for trying.