How to Absolute Pos. Website with no gap at top and don't lose left side of page?

This problem has bugged me for a while. Using the:

margin: 0 auto;

method, YES centers it but has that annoying bloody gap at the top of the page!

However the absolute positioning method:

#html, #body {

height: 100%;

margin: 0;

padding: 0;

padding-left: 1px;

border: 0;

}

#MainCont {

width: 900px;

height: auto;

border: 2px solid #BACFCF;

margin: 0;

margin-right: -450px;

padding: 0;

position: absolute;

top: 0px;

right: 50%;

text-align: left;

}

with the push 50% then subtract half the width in the margin centers the page, removes the gap but for all i try when the page becomes small enough for scroll bars starts losing the left side.

I use this method as i figure most circumstances size wont go bellow 900px but it bugs me and id like to get it so as it stops at the edge and scrolls properly.

Any ideas? I'd really love this solved.