JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html>

 <head>

   <meta http-equiv="Content-Type"
         content="text/html; charset=ISO-8859-1" />

    <title>Evaluaci&oacute;n de Curso</title>

    <style type="text/css">
    body {
        background-color: #CC7722;
        margin-left:20%;
        margin-right:20%;
        border:3px dotted gray;
        padding: 10px 10px 10px 10px;
         font-family:sans-serif;

    }


    .tabla img {
        width:100%;
    }

 </style>

 </head>

<body>





    <!--div class="tabla">
<table>
<tr>

<td width="331*">
<img src='http://img690.imageshack.us/img690/4338/softrain2.jpg' width="300" height="123" border='0'/>
</td>

<td width="331*">
<img src='http://img204.imageshack.us/img204/671/oportuniti.png' width="300" height="123" border='0'/>
</td>

<td width="331*">
<img src='http://img530.imageshack.us/img530/4852/easytest.png'  width="300" height="123" border='0'/>
</td>

</tr>
</table>
</div-->






<img src='http://img690.imageshack.us/img690/4338/softrain2.jpg' width="408" height="123"border='0'/>








<h1>Evaluaci&oacute;n</h1>


<p>Por favor, tome unos minutos para llenar esta evaluaci&oacute;n. </p>

<p> </p>

<form action="script.php" method="post">

    <p> 

        <!--h3>Info Personal</h3-->
        <table>


        <tr><td>Nombre y Apellido:</td> <td> <input type="text" name="nombreYapellido" value="" /> </td></tr>


        <tr><td>Empresa:</td> <td> <input type="text" name="empresa" value="" /> </td></tr>

        <tr><td>E-mail:</td> <td><input type="text" name="email" value="" cols="234" /> </td></tr>

       </table> 




        <h2>Curso</h2>

       <table> 
       <tr>
        <td>Nombre del Curso:</td> 
        <td>
        <select name="cursoTomado">
          <option value="NA"></option>

          <option value="AdminLinux">Administraci&oacute;n Linux</option>
          <option value="AJAX">AJAX</option>
         ...

JavaScript

$(document).ready(function(){
  $(":checkbox").change(function(){
    if ($("[name="+this.name+"]").filter(":checked").length>3) {
      alert("Warning! You've selected more than three options.");
    }
  });
});