Question

What is the difference between
margin-left: 10px; and position: relative; left: 10px;?

It seems to produce the same result

Answer 1

When you move something with position:relative you’re not actually moving the space it takes up on the page, just where it is displayed.

An easy way to test this is to use a simple structure like this:

<div id = "testbox">
  <img src = "http://www.dummyimage.com/300x200" id = "first">
  <img src = "http://www.dummyimage.com/300x200" id = "second">
</div>

with the following CSS:

img{ display:block; }
#first{ margin-top:50px; }

versus this CSS:

img{display:block;}
#first{position:relative; top:50px;}

You’ll see that the first moves everything down 50px while the second only moves the first image down (which means it will overlap the second image).

Edit: you can check it out in action here: http://www.jsfiddle.net/PKqMT/5/

Comment out the position:relative; and top:100px; lines and uncomment the margin-top line and you’ll see the difference.