How to center the page div container?

HTML & CSS
1

The main page div container isn’t centering when I add float: center to the CSS.
When I add something like this in the CSS margin: 150px;
It’ll be centered in IE8 on my PC, but not centered in IE8 on a laptop.
Help please

2

There’s no such thing as float:center. If you want to centre a block level element, give it a width and margin:0 auto.