How to adjust sidebar

These are the three classes dimensions inspected in Chrome:

#leftcontent, #twocol, #threecol, #threecol2, .commentlist {
width: 456px;
}

#sidebar {
width: 180px;
}

#secondsidebar {
width: 300px;
}

You could tweak them up. However, I see that the latest changes have been accessible from the header inline style which is probably generated from the theme and it overrides the style.css changes. Check for some text either in your header.php or some function generator that generates “body{width:1024px;}#mainwrapper{width:1004px;}…” (and more inline) and update there (or delete that all and use the proper style.css only)