Remove margins and paddings from the block level elements before styling
 
 

When you are aiming for cross-browser support, doing lots of positioning and/or want a pixel-perfect layout.

Some browsers have a default padding and margin for certain elements/tags, like for the <h1> or <p> or <ul>. The simplest way to overcome such a problem before even starting styling your document is to use the following code:

* {
margin:0;
padding:0;
}

The asterisk is a universal selector that sets /all/ elements to 0.