Please look at following html...
.wrapper {
position: relative;
}
.mydiv1 {
margin-left: -10px;
margin-top: -10px;
}
<div class="wrapper">
<div class="mydiv1">div1</div>
</div>
.mydiv1
was pulled left as 10px
and through out it's parent's left border.
But nothing happens on its top.
Why did it work differently?