Font-Awesome/scss/_bootstrap.scss

/* BOOTSTRAP SPECIFIC CLASSES
 * -------------------------- */

/* Bootstrap 2.0 sprites.less reset */
[class^="icon-"],
[class*=" icon-"] {
  display: inline;
  width: auto;
  height: auto;
  line-height: normal;
  vertical-align: baseline;
  background-image: none;
  background-position: 0% 0%;
  background-repeat: repeat;
  margin-top: 0;
}

/* more sprites.less reset */
.icon-white,
.nav-pills > .active > a > [class^="icon-"],
.nav-pills > .active > a > [class*=" icon-"],
.nav-list > .active > a > [class^="icon-"],
.nav-list > .active > a > [class*=" icon-"],
.navbar-inverse .nav > .active > a > [class^="icon-"],
.navbar-inverse .nav > .active > a > [class*=" icon-"],
.dropdown-menu > li > a:hover > [class^="icon-"],
.dropdown-menu > li > a:hover > [class*=" icon-"],
.dropdown-menu > .active > a > [class^="icon-"],
.dropdown-menu > .active > a > [class*=" icon-"],
.dropdown-submenu:hover > a > [class^="icon-"],
.dropdown-submenu:hover > a > [class*=" icon-"] {
  background-image: none;
}


/* keeps Bootstrap styles with and without icons the same */
.btn, .nav {
  [class^="icon-"],
  [class*=" icon-"] {
    //    display: inline;
    &.icon-large { line-height: .9em; }
    &.icon-spin { display: inline-block; }
  }
}
.nav-tabs, .nav-pills {
  [class^="icon-"],
  [class*=" icon-"] {
    &, &.icon-large { line-height: .9em; }
  }
}
.btn {
  [class^="icon-"],
  [class*=" icon-"] {
    &.pull-left, &.pull-right {
      &.icon-2x { margin-top: .18em; }
    }
    &.icon-spin.icon-large { line-height: .8em; }
  }
}
.btn.btn-small {
  [class^="icon-"],
  [class*=" icon-"] {
    &.pull-left, &.pull-right {
      &.icon-2x { margin-top: .25em; }
    }
  }
}
.btn.btn-large {
  [class^="icon-"],
  [class*=" icon-"] {
    margin-top: 0; // overrides bootstrap default
    &.pull-left, &.pull-right {
      &.icon-2x { margin-top: .05em; }
    }
    &.pull-left.icon-2x { margin-right: .2em; }
    &.pull-right.icon-2x { margin-left: .2em; }
  }
}