Edited your JSFiddle: http://jsfiddle.net/n264v/3/
Also, the following code works too:
$(".viewPrices").click(function () {
$(".viewPrices").parent().siblings('.list').toggleClass('visible');
});
For this HTML:
<div class="container">
<div class="box">
<h2>Langtidsparkering</h2>
<div class="content">
Lorem ipsum dolor sit amet..
</div>
</div>
<div class="listcontainer">
<div class="list"> (THIS DIV SHOULD GET A CLASS "VISIBLE", WHEN THE BUTTON IS CLICKED)
</div>
<div class="listbar">
<button class="viewPrices" type="submit" title="Open">Se priser<span></span </button>
</div>
</div>
</div>
Took the liberty to add the following css:
.list{
display:none;
}
.visible{
display:block !important;
}
JSFiddle for the above sample