您需要添加position: absolute 到您的Facebook按钮。

Header.php

<div class="logo"> 
 <a class="logoimga" title="Gelnagels Gina" href="http://www.gelnagels-gina.be/">
   <img src="http://www.gelnagels-gina.be/wp-content/uploads/2015/04/Gina4.png">
 </a>
 <a class="header-img-1" title="Facebook-header" href="#">
   <img src="http://www.gelnagels-gina.be/wp-content/themes/optimizer/facebook.png">
</a>
</div>

CSS

.header-img-1 {
    left: 15%;
    position: absolute;
    top: 50px;
}