In many of Chris’ videos the margin:0 auto; statement is referred to as a "Trick". So I went off on a search to find out why this "Trick" works. Looking at http://www.w3schools.com/CSS/css_margin.asp I see that auto simply means let the browser set the margin. But I don’t understand why the preceeding 0 is required.
I know that margin:0 simply means set all 4 sides to 0. But what does it mean when you put a space between 0 and auto?