Register popup PHP help

When my website is visited there is two buttons. One that says register and one that says login. When pressed a CSS popup will appear. Im trying to make this popup work for the register. How would i do this? here is the code

[CODE] <a href=”#x” class=”overlay” id=”join_form”></a>
<div class=”popup”>
<h2>Sign Up</h2>
<p>Please enter the details you would like to<br>
register with here. You MUST be <br>atleast thirteen
to register.</p><br>

<div>
<label for=”email”>Email</label>
<input type=”text” id=”email” value=”” />
</div>
<div>
<label for=”pass”>Password</label>
<input type=”password” id=”pass” value=”” />
</div>
<div>
<label for=”firstname”>First name</label>
<input type=”text” id=”firstname” value=”” />
</div>
<div>
<label for=”lastname”>Last name</label>
<input type=”text” id=”lastname” value=”” />
</div>
<div>
<label for=”sex”>Sex</label>
<input type=”radio” name=”sex” value=”male”>Male
<input type=”radio” name=”sex” value=”female”>Female
</div>[/CODE]

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