makes labels go inside an input tag

index.html

<form action="/message">
    <p>
      <label for="user_tel">Telephone:</label>
      <input type="text" id="user_tel"><br />
    </p>
    <p>
      <label for="user_msg">Message:</label>
      <textarea name="" id="user_msg" cols="30" rows="10">

      </textarea><br />
    </p>
  <input type="submit" value="Absenden">
</form>

labelinside.js

$('label').addClass('labelinside');

$('label').closest('p').find('input, textarea')
  .on('focus', function() {
    $(this).prev().animate({'opacity': '0.5'}, 100);
    $(this).on('keydown', function() {
      $(this).prev().hide();
    });
  })
  .on('blur', function() {
    $(this).prev().animate({'opacity': '1'}, 100);
    if($(this).val() === '') {
      $(this).prev().show();
    }
  })

style.css

.labelinside {
  position: absolute;
  padding: <some padding>;
  color: #000;
}