footer section getting bumped up into elements above it - footer

Question

I'm relatively new to web designing so hopefully what I'm writing here makes sense . . .
I have three sections on my page. A header, the middle section and the footer. Within the middle section there are three divs which include an image and text and each taking up 30% of the width of the entire middle section. When the page is decreased to smaller sizes, the footer bumps up onto this middle section. Of course, I'm wanting the footer section to remain at the bottom and be responsive.
At first I had these three divs floated left and I thought this may have something to do with the footer moving. But then I changed the divs to an inline-block.
I've also tried to clear: both. The footer keeps moving up when I scale down the page.
Hopefully, I'm making sense and someone can help. Thanks.
HTML:
<section class='mid-section'>
<div class='one-third'>
<a href='thai-tattoo.html'><img src='https://farm2.staticflickr.com/1528/26102511281_67fdc7c189_m.jpg' alt='Bangkok street'></a>
<h3>HEADLINE</h3>
<p>TEXT</p>
</div>
<div class='one-third'>
<a><img src='http://gratisography.com/pictures/264_1.jpg'><h3>HEADLINE</h3><p>TEXT</p>
</div>
<div class='one-third'>
<a><img src='http://gratisography.com/pictures/264_1.jpg'><h3>HEADLINE</h3><p>TEXT</p>
</div>
</section>
<div class='bottom-section'>
<div class='social-icons'>
<p > Follow us on the Web </p>
</div>
</div>
CSS:
.one-third {
width: 30%;
display: inline-block;
margin: 5% 0 0 2.5%; }
.one-third img {
width: 100%;
height: 300px; }
.one-third p {
margin: 0.5em; }
.tattoo-text {
width: 60%;
margin: 50px; }
.tattoo-h {
font-size: 25px; }
.tattoo-pic {
width: 60%;
float: right;
margin: 10px; }
.quaint-street-pic {
width: 60%;
float: left;
margin: 10px;
height: 300px; }
.social-icons {
float: right;
margin: 100px 100px 0 0; }