The location should adjust the size automatically to make all icons fit on the Navigation Toolbar.
If that isn't the case then an extension may be causing it.

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.com/kb/Safe+Mode

Use code like this in userChrome.css to set a max-width for those bars:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */

#urlbar-container { max-width: 400px !important; }
#search-container { max-width: 200px !important; }

Putting in the '@namesapace url......uxl");' and the code:

1. urlbar-container { max-width: 600px !important; min-width: 600px !important; }
2. search-container { max-width: 200px !important; min-width: 200px !important; }

made no difference.

When in 'customize toolbar' the cursor changed to the drag hand whenever over the 'dead' space left by sortening the url container and removing the serch container ie. the original space alocated to hold both container.

Running in safe mode made no difference. Disabling all the add-ons (except ChromeEdit) and all the plug-ins and restarting Firefox made no difference; the 'dead space' still exists.

The images I've uploaded are of the customize toolbar stage and the 'done' result.

I'll keep trying

Have solved it! Or, at least, identified the problem. Whenever the bookmark icon is included it seems to effect the behaviour of the other icons as well as failing to display itself (the bookmark icon). By not including the bookmark icon all is well.

I have tried the max and min width 10px either side of a median value but reset so max and min are the same value. Performed as expected in both cases. Not including the min values made no difference. Have enable the 8 add-ons and the 19 plug-ins. All are performing as normal.

Back to normal using the bookmarks menu when I want to bookmark a page.

Thanks for the input.

That code works for me.

#urlbar-container { max-width: 400px !important; }
#search-container { max-width: 200px !important; }

Do you have other code in userChrome.css that may cause it to fail?

Can you post the full content of userChrome.css in <pre>xxxx</pre> tags?

This is my userChrome.css file:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

#urlbar-container {max-width: 600px !important;}
#search-container {max-width: 600px !important;}

Prior to being unable to customize the tool bar I had no active userChrome.css. I viewed the example userChrome.css and copied over to the firefox directory and then left only the code that related to the container width. With it in place I could control the width of the url and search containers (but not when trying to include the bookmark icon).

I don't use the toolbar search facility so the search-container code is not employed.

Any advice on how to hone the userChrome.css would be appreciated.