Can't move logo position

New to web design, so this is probably really badly written code. This may be something very obvious, but no matter what i change in the css of the logo, i can't get it to move? I need to move the logo down.

<div class="header" id="myHeader">
    <div class="logo">
        <img src="img/sweme.png" width=300 height=90>
    </div>

CSS

.header {
    padding: 10px 16px;
    background-color: darkred;
    box-shadow: 0px 10px 20px black;
    font-family: arial;
    position: relative;
    height: 90px;
}

.logo {
    position: absolute;
    float: left;
    margin-top: 50px;
}