On: Firefox 29

[ubercow13]

You can reduce it because yes it is useless. Something like this (one of these is pointless but I can't remember which one..)

  /* correct titlebar icons position */
  #titlebar-content > * {
    margin-top: -6px;
  }

  /* Reduce the padding between the URL bar and the tabs/content */
  #nav-bar-customization-target {
    margin-top: -2px !important;
    margin-bottom: -2px !important;
  }

[steamer25 → ubercow13]

Presumably (for the uninitiated) under userchrome.css? http://www-archive.mozilla.org/unix/customizing.html

[ubercow13 → steamer25]

Yes or using Stylish which has an option to add chrome style scripts