Body text goes over the top of fixed nav bar

This is usually caused by your z-index, make sure you put:

CSS

z-index: 500 // or whatever number that is a positive real number.

Yep, I was right, see this DEMO.

nav {
    background-color: #262626;
    height: 60px;
    z-index:1; //any higher integer value
    width: 100%;
    position: fixed;
    top: 0;
    bottom: 0;
    -webkit-box-shadow: 0px 0px 8px 0px #000000;
    -moz-box-shadow: 0px 0px 8px 0px #000000;
    box-shadow: 0px 0px 8px 0px #000000;
}

Refer z-index in W3Schools also Refer CSS-Tricks