jQuery: playing with the siblings() method

HTML

<div class="header"></div>

<img src="https://www.facebook.com/tr?id=1464338023867789&amp;ev=PageView&amp;noscript=1">

<img src="https://lh4.googleusercontent.com/-l8Ji4wDA2c4/T1Mra5NRiTI/AAAAAAAAA3o/PHbTLTwSMjA/s425/code-programming.jpg" />

CSS

#gallery {
    width: 600px;
    margin: 2em auto;
    overflow: hidden;
}

#gallery img {
    float: left;
    width: 195px;
    margin-right: 5px;
    margin-bottom: 5px;
    height: 150px;
    cursor: pointer;
    position: relative;
}

JavaScript

$(".header").next("img").css("display","none");