Strange extra top space in body

Try this in css:

h1 {
    margin-top: 0;
}

This is a common scenario (logo image wrapped in h1 tag):

I believe this is actually caused by the margin on your h1 element.

My console is showing a 0.67em top margin on the <h1> surrounding your top element.

Try this...

h1 {
    margin: 0;
}