Change searchbar width in FireFox

Change the width of the Search Bar

By default, the Search bar on the toolbar is relatively small. To
specify your own width in pixels, add the following code to your userChrome.css file:

/* Make the Search box flex wider
  (in this case 400 pixels wide) */
#search-container, #searchbar {
  -moz-box-flex: 400 !important;
}