Is this about the History Sidebar (Ctrl+H) or about the History Manager (Library)?

Try to open a new window in case there is a problem with the current window if toy use the sidebar.

You can check for problems with the places.sqlite database file in the Firefox profile folder.

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

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/

History Sidebar (Ctrl+H). I solved it by choosing History > Show All History, meaning that I can see a full page of history with sites and dates. But why does the History Sidebar allow you to get a double-arrow icon when pausing the cursor along the edge, but not allow you to use it to change the size of the sidebar panel? Thanks.

There is a minimum (min-width: 14em;) and maximum (max-width: 36em;) for the sidebar and you can't drag the resizer icon beyond that limit.

Add code to the userChrome.css file below the default @namespace line.

• http://kb.mozillazine.org/userChrome.css

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

#sidebar { min-width:0px !important; max-width:none !important; }

The customization files userChrome.css (user interface) and userContent.css (websites) are located in the chrome folder in the Firefox profile folder.

• http://kb.mozillazine.org/Editing_configuration

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)

• Create the chrome folder (lowercase) in the <xxxxxxxx>.default profile folder if this folder doesn't exist
• Use a plain text editor like Notepad to create a (new) userChrome.css file in the chrome folder (file name is case sensitive)
• Paste the code in the userChrome.css file in the editor window
• Make sure that the userChrome.css file starts with the default @namespace line
• Make sure that you select "All files" and not "Text files" when you save the file via "Save file as" in the text editor as userChrome.css.
  Otherwise Windows may add a hidden .txt file extension and you end up with a not working userChrome.css.txt file

Thanks! Great response, I appreciate it.