Adjusting Grid Width

I am trying to widen the grid on this page to include all three columns. Here is the code to the grid, any advice would be greatly appreciated.

/* Grid Style */
#main-content #grid{width:1500px ; margin-left:5px;margin-right:5px;}, #main-content #content{margin: 10px 0px 10px 0px; padding:2px;}

#filters{float:left; border-bottom: 1px dotted #CCC; overflow:hidden;margin-top:0px; padding-left:10px;}
#filters li{float:left; margin:0px 0px 0px 0px;padding: 8px 8px 8px 8px;}
#filters li a {
	text-decoration: none;
	text-transform: none;
	line-height: 12px;
	color: black;
	background-color:rgba(255,255,255,0.9);
	float: left;
	padding:8px 8px 8px 8px;
	font-size:16px;
	-moz-border-radius: 10px;
	-webkit-border-radius:10px;
	border-radius:5px;
}
#filters li.current a, #filters li a:hover {
	color: white;
	background:rgba(0,191,255,0.9);
	-moz-border-radius: 10px;
	-webkit-border-radius:10px;
	border-radius:10px;
}

#main-content .item-list {
	background-color:rgba(255,255,255,0.9);
	border-radius: 5px;
	-moz-border-radius: 5px;
	-webkit-border-radius: 5px;
	box-shadow: 2 2px 6px rgba(128,128,128,0.9);
	-moz-box-shadow: 0 2px 3px rgba(128,128,128,0.8);
	-webkit-box-shadow: 0 2px 3px rgba(128,128,128,0.8);
	overflow:hidden;
	margin:20px 15px 20px 0px;
	width:350px;
	float:clear:both;
}