Because the vertical-align
is set at baseline as default.
Use vertical-align:top
instead:
.small{
display: inline-block;
width: 40%;
height: 30%;
border: 1px black solid;
background: aliceblue;
vertical-align:top;
}
http://jsfiddle.net/Lighty_46/RHM5L/9/
Or as @f00644 said you could apply float
to the child elements as well.