Autofocus Navigation

Please help – I want a horizontal navigation under the header/logo and a background color with width 800px. This is the current code. Is there a simple way to change this?

/* =header */
#header {margin:55px 0 0;height:105px;text-transform:normal;width:600px;clear:none;float:left ;}
#header a:hover{text-decoration:none;color:#888;}
#header h1 {font-size:1.8em;line-height:0.8em;padding:5px 0 0;}
#header h1 a{font-weight:100;letter-spacing:-0.05em;position:relative;}
#header #blog-description {color:#888;}
#access {display:table;height:160px;vertical-align:middle;width:200px;float:right;}
#access #menu {vertical-align:middle;display:table-cell;font-size:0.8em;}
#access #menu ul {vertical-align:middle;display:block}
#access #menu ul li ul {margin-left:10px;}
#access #menu a{font-weight:800;}