bootstrap-float-label.css

.has-float-label {
  display: block;
  position: relative;
}
.has-float-label label, .has-float-label > span {
  position: absolute;
  left: 0;
  top: 0;
  cursor: text;
  font-size: 75%;
  opacity: 1;
  -webkit-transition: all .2s;
          transition: all .2s;
  top: -.5em;
  left: 0.75rem;
  z-index: 3;
  line-height: 1;
  padding: 0 1px;
}
.has-float-label label::after, .has-float-label > span::after {
  content: " ";
  display: block;
  position: absolute;
  background: white;
  height: 2px;
  top: 50%;
  left: -.2em;
  right: -.2em;
  z-index: -1;
}
.has-float-label .form-control::-webkit-input-placeholder {
  opacity: 1;
  -webkit-transition: all .2s;
          transition: all .2s;
}
.has-float-label .form-control::-moz-placeholder {
  opacity: 1;
  transition: all .2s;
}
.has-float-label .form-control:-ms-input-placeholder {
  opacity: 1;
  transition: all .2s;
}
.has-float-label .form-control::placeholder {
  opacity: 1;
  -webkit-transition: all .2s;
          transition: all .2s;
}
.has-float-label .form-control:placeholder-shown:not(:focus)::-webkit-input-placeholder {
  opacity: 0;
}
.has-float-label .form-control:placeholder-shown:not(:focus)::-moz-placeholder {
  opacity: 0;
}
.has-float-label .form-control:placeholder-shown:not(:focus):-ms-input-placeholder {
  opacity: 0;
}
.has-float-label .form-control:placeholder-shown:not(:focus)::placeholder {
  opacity: 0;
}
.has-float-label .form-control:placeholder-shown:not(:focus) + * {
  font-size: 150%;
  opacity: .5;
  top: .3em;
}

.input-group .has-float-label {
  -webkit-box-flex: 1;
  -webkit-flex-grow: 1;
      -ms-flex-positive: 1;
          flex-grow: 1;
  margin-bottom: 0;
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
  -webkit-flex-direction: column;
      -ms-flex-direction: column;
          flex-direction: column;
  -webkit-box-pack: center;
  -webkit-justify-content: center;
      -ms-flex-pack: center;
          justify-content: center;
}
.input-group .has-float-label .form-control {
  width: 100%;
  border-radius: 0.25rem;
}
.input-group .has-float-label:not(:last-child), .input-group .has-float-label:not(:last-child) .form-control {
  border-bottom-right-radius: 0;
  border-top-right-radius: 0;
  border-right: 0;
}
.input-group .has-float-label:not(:first-child), .input-group .has-float-label:not(:first-child) .form-control {
  border-bottom-left-radius: 0;
  border-top-left-radius: 0;
}