To center an element you need three things:
- a valid DocType
- an element with a width
- that elements right/left margins set to auto
Your .fadecontentwrapper already has a width so adding
margin: 0 auto;
to that will center it.
But the content doesn't follow along with it because it's absolutely positioned. Do you really need ap there? Have a look at the pitfalls of absolute positioning
to .fadecontentwrapper will make the ap elements it contains position themselves relative to .fadecontentwrapper instead of the body of the document.
You get the scrollbars because you add padding to 800px width .fadecontent. The box model shows how what you put in a container must not exceed the size of that container - margin/padding/border all count when figuring total width.