[html] How do I horizontally center an absolute positioned element inside a 100% width div?

here is the best practiced method to center a div as position absolute

DEMO FIDDLE

code --

#header {
background:black;
height:90px;
width:100%;
position:relative; // you forgot this, this is very important
}

#logo {
background:red;
height:50px;
position:absolute;
width:50px;
margin: auto; // margin auto works just you need to put top left bottom right as 0
top:0;
bottom:0;
left:0;
right:0;
}