CSS problem.
It works fine in Firefox.
Install Firefox. Then add the "Firebug" addon. Turn it on and play with it and you will see where the problem is in your CSS.
#custom-doc {
margin:auto;
min-width:875px;
text-align:left;
width:67.31em;
}
/*site-map.html (line 9)*/
#doc, #doc2, #doc3, #doc4, .yui-t1, .yui-t2, .yui-t3, .yui-t4, .yui-t5, .yui-t6, .yui-t7 {
margin:auto;
text-align:left;
width:57.69em;
}