You have to find a file called userchrome-example.css in your user profile.
It will be in the document and settings folder of Windows XP machines with a path similar to this -
C:\Documents and Settings\[User Name]\Application Data\Mozilla\Firefox\Profiles
Firefox creates the file called userchrome-example.css in that folder. It doesn't do anything until you change it.
You will need to open the file userchrome-example.css with a text editor and paste this code -
/* Make the Search box flex wider
(in this case 400 pixels wide) */
#search-container, #searchbar {
-moz-box-flex: 400 !important;
}
Rename the file userchrome.css and you should have a nice sized Google toolbar when you restart Firefox.
