How to force div to be bottom using bootstrap - html

Question

I'm using bootstrap on Codepen.io.
I have a page divided into 3 main divs. The middle div has 3 images and is divided into 3 columns.
Everything looks fine on desktop but once I resize the window, the bottom div overlaps the third image instead of moving to the bottom.
Is there a way to make bootstrap work its magic without changing CSS manually?
https://codepen.io/oldmanwithbeer/pen/ENzvoY?editors=1000#0
<div class="container-fluid">
<div class="row">
<div id="one" class="col-md-12">
<div id="btn_row" class="row">
<div class="col-md-12 text-center">
<button type="button" class="btn btn-primary">some text</button>
<button type="button" class="btn btn-primary">some text</button>
<button type="button" class="btn btn-primary">some text</button>
<button type="button" class="btn btn-primary">some text</button>
</div>
</div>
</div>
</div>
<div class="row">
<div id="two" class="col-md-12">
<h2>some text</h2>
<div class="row">
<div class="col-md-4">
<div class="thumbnail">
<a href="#" target="_blank">
<img class="img-responsive" src="#" alt="text"></a>
<div class="caption">some text</div>
</div>
</div>
<div class="col-md-4">
<div class="thumbnail">
<a href="#" target="_blank">
<img class="img-responsive" src="#" alt="text"></a>
<div class="caption">some text</div>
</div>
</div>
<div class="col-md-4">
<div class="thumbnail">
<a href="#" target="_blank">
<img class="img-responsive" src="#" alt="text"></a>
<div class="caption">some text</div>
</div>
</div>
</div>
</div>
</div>
<div class="row">
<div id="three" class="col-md-12"><h3>text</h3>
</div>
</div>
</div>

Answer 1

Actually for the proper responsive or mobile view developers use the css media query. If you look at the bootstrap doc then you may see the demonstration. Importantly you used fixed height in different elements like:
#portfolio {
height: 400px;
}
So I recommendation is to use css media query at the bottom of your stylesheet or style with auto height. Like this:
#media only screen and (max-width: 767px) {
#portfolio {
height: auto;
}
}
Hope it will do the magic ...