Layer moving when browser resized

[stevelibby]

I have created a css layout, I now want to add a layer(box) in an absolute position if that's right. However once I resize the browser it moves, what am I doing wrong?

[stevelibby]

think i have figured it out, when centering the page with a
margin-left:auto;
margin-right:auto;

i added
position:relative

before adding my absolute style.

[legaleagle]

Ah yep that would do it :)