Why I can't applied spacing between two divs

I have 5 div, and between first and second I have spacing set on button2 class margin-top:10px; But that's applied only between second and first div, why I don't have spacing between thrid and second ... I don't know why I have little spacing between third and fourth divs.

JSFIDDLE: http://ift.tt/1bEjncm

HTML

<div class="contactdiv"><div class="ppdiv">
<button class="ppenvelope"><img src="http://ift.tt/1IVUEuw" alt="Slika"></button><button class="pptext"><span class="pptext2">PRIVATNA PORUKA</span></button>
</div><!--Zatvoren ppdiv--><div class="button2">
<button class="ppenvelope"><img src="http://ift.tt/1IVUEuw" alt="Slika"></button><button class="pptext"><span class="pptext2">PRIVATNA PORUKA</span></button>
</div><!--Zatvoren button2--><div class="button2">
<button class="ppenvelope"><img src="http://ift.tt/1IVUEuw" alt="Slika"></button><button class="pptext"><span class="pptext2">PRIVATNA PORUKA</span></button>
</div><!--Zatvoren button2--><div class="button2">
<button class="ppenvelope"><img src="http://ift.tt/1IVUEuw" alt="Slika"></button><button class="pptext"><span class="pptext2">PRIVATNA PORUKA</span></button>
</div><!--Zatvoren button2--><div class="button2"><button class="ppenvelope"><img src="http://ift.tt/1IVUEuw" alt="Slika"></button><button class="pptext"><span class="pptext2">PRIVATNA PORUKA</span></button>
</div><!--Zatvoren button2-->
</div><!--Zatvoren contactdiv-->

CSS:

.contactdiv{
    width:271px;
}
.ppdiv{
    overflow: hidden;
    margin-top:20px;
    margin-left: 20px;
}
.ppenvelope, .pptext {
    float: left;
    border: none;
    height: 48px;
}
.ppenvelope{
    border-top-left-radius: 4px;
    border-bottom-left-radius: 4px;
    background: #b2d4dd;
}
.ppdiv img{
    padding:10px;
}
.button2 img{
    padding:10px;
}

.pptext{
    border-top-right-radius: 4px;
    border-bottom-right-radius: 4px;
    background: #c9e0e6;
    color:#4c6974;
}
.pptext2{
    display: inline-block;
     color:#4c6974;
       padding-top: 13px;
       padding-bottom:13px;
       padding-left: 13px;
        padding-right: 13px;
}
.button2{
    margin-top: 10px;
    margin-left:20px;
}