How to remove "Open menu"

Question

I am using Firefox 29. I would like to remove this menu because I prefer the Menu Bar. How can I do this?

The manual way

I'm listing this first as it's the most efficient way.

1. Close Firefox.

2. Add the following code to your userChrome.css file:

   #PanelUI-menu-button
   {
       display: none !important;
   }
   

   It is located in the chrome subfolder inside your Firefox profile folder. Create one in case it doesn't exists already. Here's an example: userChrome-example.css.

   Note Apparently !important doesn't seem to be needed and could be omitted.

3. Start Firefox again.

Userstyle

If you have the Stylish add-on installed, you can use this: Hide #PanelUI-menu-button for firefox v29+.

Comments

[Zombo]

Great answer. Also it makes sense that !important is optional as I suspect you would rarely have competing chrome CSS definitions.

[Rads]

Since there was no such, I have created "userChrome.css" (with content as you wrote) inside a newly created "Chrome" folder. Then I have copied this "Chrome" folder to these two locations: - C:\Users[user]\AppData\Local\Mozilla\Firefox\Profiles - C:\Users[user]\AppData\Roaming\Mozilla\Firefox\Profiles There was no other "Profiles" folder on the whole C:\ but the "menu button" is still there. Do you have some idea what is the problem?

[and31415]

@user321719 The Firefox profile folder is usually stored in the following location in Windows Vista and later: C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<pr‌​ofileFolder>. To make things easier, press Win+R, type or paste %AppData%\Mozilla\Firefox\Profiles in the text box, and press Enter. You should see all Firefox profile folders (there's only one by default). Open the folder, and put the chrome folder there. Assuming you did it right, the changes should be applied next time you start Firefox.

[mach]

Since Firefox 69, there is a prerequisite: userChrome.css needs to be enabled in about:config, see Firefox 69: userChrome.css and userContent.css disabled by default - gHacks Tech News.