Ping coming soon page using Bootstrap

Hello there! With this challenge I've used a little Bootstrap for the form input and button, so they can smoothly move responsive when the screen resizes.

This is my first newbie JS challenge, and I'm reeeeally new to this. I've been struggling with learning Javascript so if someone have any suggestion about my code, I would really appreciate that. I feel like I used really simple DOM manipulation, I don't know if I hardcoded some things, like

else if (email == '') {
        empty.style.display="block";
        error.style.display="none";
        document.getElementById('email').style.borderColor = 'red';
        return false;
} 

I used the error.style.display="none" because if I tried submitting an invalid email and then an empty one, both errors showed up, so I feel like I hardcoded it this way. There is any way to improve this? Thanks!