Overall, a very nice effort. Just a few minor suggestions:
The black text at the top is hard to read on that background. At the least I think you need to make it completely black and bold for all the text in the header. But really, you probably need to add a background like you did for the form.
If you need to set a height on the text inputs, use ‘em’ instead of ‘px’. That way it scales nicely when the text size is increased.
However, I was able to submit a form with email “abc@a”.
Apparently, you’ve just made it so that an email contains an at symbol! See standard email format (there are standardized requirements for emails), and this could make your regexp better!