AngularJS 1.2.x

var app = angular.module('plunker', []);

<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.2.x" src="https://code.angularjs.org/1.3.0-beta.11/angular.js" data-semver="1.3.0-beta.11"></script>
    <script src="app.js"></script>
  </head>

  <body>
    <form name="form">
      <input type="email" name="firstName" ng-model="user.firstName" ng-model-options="{ debounce: 300 }">
      <span ng-show="form.firstName.$error.email">正しくないメールアドレス</span>
    </form>
  </body>

</html>

/* Put your css in here */