I got incredibly irritated at the center align issue of these new forums. So here are the fix's you need to add to center it. There are addons that you may use to do this manually, but my hope is SE implements them seeing as it takes less than 5 seconds.

html {
background:#555046 url(images/elevenb/doc_bg.jpg) repeat-y ;

}

Needs to be:

html {
background:#555046 url(images/elevenb/doc_bg.jpg) repeat-y ;
background-position:top center;
}

And:

body {
width:910px;
min-width:650px;
max-width:auto;
margin: 38px 0px 0px 57px;
font-size:13px;
color:#3e3e3e;
line-height:1.230;
}

Needs to be:

body {
width:910px;
min-width:650px;
max-width:auto;
margin: 38px 0px 0px 57px;
font-size:13px;
color:#3e3e3e;
line-height:1.230;
margin-left: auto;
margin-right: auto;
}

Tested in Chrome 10.

Hope you can implement these changes