Form and email validation with JS

I'm not sure if the warning messages hide and show is done in an optimal way, I think it could be developed in a better way. In my personal desktop the original zoom of the page looks a little big, I don't know if it's normal if I designed the page to a width of 1440px and height of 1024px. Just a couple of differences (margins, paddings, etc) between the original design and my solution. Any advice or feedback will be welcome.