You also have some stray <em> tags below:
You may want to consider changing to:
<button type="submit" class="submit">submit<em></em></button>
<input class="submit" type="submit" value="submit" />
Also note the type="email" attribute. In modern browsers that will trigger an automatic validation of that input. In mobile browsers (well at least iPhone Safari ) it will also bring up the keyboard with the @ and .com keys. Cool stuff.
<input type="email" name="email" placeholder="Your email:" />