Re-Center Webpage in CSS/HTML

Re-Center Webpage in CSS/HTML

I have custom built CSS for me but am no longer in contact with the
creator. I wanted to make a div (#rightcolumn) bigger by 55px. I did this
by making iframe in the div bigger and it auto expands for me. However the
banner, (#topsection), became a little short - so I had to add 55px to
that to make it 1255px width.
Now page is off center some. When I try to edit other float commands to
fix, the div's end up all over. I've tried for a few days. If anyone could
help now with re-centering this. I would really appreciate.
Test page: Serious Sports Bigger Link to css: CSS link New Css
body{margin:0;padding:0;line-height:1.5em;background:#C0C0C0;}b{font-size:110%;}em{color:red;}#maincontainer{width:1200px;margin:0
auto;}#topsection{background:#191919;height:90px;width:1255px}#contentwrapper{float:left;width:100%;}#contentcolumn{margin:0
360px 0
180px;color:#F1F1F1;}#leftcolumn{float:left;width:180px;margin-left:-1200px;background:#C8FC98;}#rightcolumn{float:left;width:355px;margin-left:-355px;background:#E5E5E5;}#footer{clear:left;width:100%;background:#191919;color:#FFF;text-align:center;padding:4px
0;}#footer
a{color:#62C301;}.innertube{margin:10px;margin-top:0;}.arrowgreen{width:180px;border-style:solid
solid none
solid;border-color:#94AA74;border-size:1px;border-width:1px;}.arrowgreen
ul{list-style-type:none;margin:0;padding:0;}.arrowgreen li a{font:bold
12px
Verdana,Arial,Helvetica,sans-serif;display:block;background:transparent
url(http://i39.tinypic.com/2r2rhnc.gif) 100% 0;height:24px;padding:4px 0
4px 10px;line-height:24px;text-decoration:none;}.arrowgreen li
a:link,.arrowgreen li a:visited{color:#5E7830;}.arrowgreen li
a:hover{color:#26370A;background-position:100% -32px;}.arrowgreen li
a.selected{color:#26370A;background-position:100% -64px;}