Input types + required attribute
Try to submit the form without filling the fields. You should get a notice to fill out the fields properly. Placeholders and validation completely works without JavaScript. Keep in mind: using the required attribute is client side validation only! Never forget to also validate your form on server side.
Note: Both Opera (11.11) and Safari (5.0.4) show the placeholder attribute but don't care about the required attribute and let you send the form even if the fields aren't filled. IE9 ignores both.