CSS/HTML fixed nav bar overlapping content

Question

I have made a nav bar that sticks to the top of the page, but it is sticking to some of the content and I have tried using margin-top: 100px; in the CSS file but that just moves the nav bar down 100px. Anyone have any ideas? Link to js fiddle

CSS

.con {
    overflow: hidden;
    background: #159B00;
    width: 1000px;
    height: 376px;
    border-radius: 10px;
    border: 2px solid black;
    box-shadow: 0 4px 8px black;
}
.nav {
  padding-top: 0px;
  background: #fff;
  height: auto;
  width: 100%;
  z-index: 150;
  top: o;
  position: fixed;
  box-shadow: 0 2px 3px rgba(0,0,0,.4);
}

HTML

        <div class="nav">
            <div id="nav_wraper">
                <ul>
                    <li><a href="RUN ME.html">
                        </div> 
                        </a></li>       
                        </a>
                        </li><li>
                        <a href="index.html">Home</a>
                        </li><li>
                        <a href="#">Designs&#x25BC;</a>
                            <ul>
                            </ul>
                        </li><li>
                        <a href="#">About&#x25BC;</a>
                            <ul>
                            </ul>
                        </li><li>
                        <a href="#">Contact&#x25BC;</a>
                            <ul>
                            </ul>
                        </li>
                    </ul>
                </div>
        </div>
        <main>
            <div id="iG" class="con" >
                <img src="slider.png" alt="" />
                <img src="step_1.png" alt="" />
                <img src="step_2.png" alt="" />
                <img src="step_3.png" alt="" />
                <img src="slider.png" alt="" />
            </div>
        </main>

Thanks.

Answer 1

You can fix this by adding

body{
 padding-top:100px;
}

and you have syntax error in

.nav{
 top:o; 
}

should be

.nav{
 top:0;
}

updated fiddle