console
$('.utilities a + a').click(function(){
$('.login').toggle();
$('.regist').toggle();
});
<body class="bg-green-800">
<div class="relative w-80 m-auto mt-24 p-5 rounded-md bg-gradient-to-t from-green-700 to-green-600 drop-shadow-2xl">
<div class="login">
<h2 class="mb-4 text-xl text-white font-bold font-serif">Log In</h2>
<fieldset class="mb-3 shadow-inner">
<input class="w-full h-3 py-4 px-4 text-sm placeholder-green-500 bg-green-700 border border-green-800 rounded-b-none rounded-t-md outline-none focus:bg-green-600" type="email" placeholder="Email" />
<input class="w-full h-3 py-4 px-4 text-sm placeholder-green-500 bg-green-700 border border-green-800 rounded-t-none rounded-b-md outline-none focus:bg-green-600" type="password" placeholder="Password" />
</fieldset>
<input class="w-full py-3 text-sm font-bold bg-gradient-to-b from-yellow-400 to-yellow-500 rounded-md shadow-md cursor-pointer hover:opacity-90" type="submit" value="Log In" />
<div class="utilities flex justify-between mt-5">
<a class="text-green-300 text-xs hover:text-white" href="#">Forgot Password?</a>
<a class="text-green-300 text-xs hover:text-white" href="#">Sign Up →</a>
</div>
</div>
<div class="regist">
<h2 class="mb-4 text-xl text-white font-bold font-serif">Sign Up</h2>
<fieldset class="mb-3 shadow-inner">
<input class="w-full h-3 py-4 px-4 text-sm placeholder-green-500 bg-green-700 border border-green-800 rounded-b-none rounded-t-md outline-none focus:bg-green-600" type="text" placeholder="Username" />
<input class="w-full h-3 py-4 px-4 text-sm placeholder-green-500 bg-green-700 border border-green-800 rounded-t-none rounded-b-none outline-none focus:bg-green-600" type="email" placeholder="Email" />
<input class="w-full h-3 py-4 px-4 text-sm placeholder-green-500 bg-green-700 border border-green-800 rounded-t-none rounded-b-md outline-none focus:bg-green-600" type="password" placeholder="Password" />
</fieldset>
<input class="w-full py-3 text-sm font-bold bg-gradient-to-b from-yellow-400 to-yellow-500 rounded-md shadow-md cursor-pointer hover:opacity-90" type="submit" value="Sign Up" />
<div class="utilities flex justify-between mt-5">
<a class="text-green-300 text-xs hover:text-white" href="#">Made with by zs2013</a>
<a class="text-green-300 text-xs hover:text-white" href="#">Log In →</a>
</div>
</div>
</div>
</body>
.regist {
display: none;
}