I'm trying to center an img in a div without success and I have tried many CSS hacks. I'm missing something and I have no idea what I'm doing wrong.
Markup
<div class="col-md-6">
<div class="row">
<div class="col-md-4" >
<div class="img-guarantee">
<img src='img/clock.png' class='img-responsive'>
</div>
</div>
</div>
</div>
CSS
.img-guarantee img{
display: inline-block;
margin: 0 auto;
}