I have a content pane called 'contentpane' that I need to left justify for on large monitors it stretches and a large gap shows up...  Below is the code to my .ascx file.  How do I left justify the content pane?  Below my .ascx is my .css

<%@ Control language="vb" CodeBehind="~/admin/Skins/skin.vb" AutoEventWireup="false" Explicit="True" Inherits="DotNetNuke.UI.Skins.Skin" %>
<%@ Register TagPrefix="dnn" TagName="LOGO" Src="~/Admin/Skins/Logo.ascx" %>
<%@ Register TagPrefix="dnn" TagName="JDMENU" Src="~/DesktopModules/JDMENU/JDMENU.ascx" %>

<div id="skinall">
    <div class="skinleft">
        <div class="skinlogo"><dnn:LOGO runat="server" id="dnnLOGO" /></div>
        <div class="skinmenu"><dnn:JDMENU runat="server" id="dnnJDMENU" /></div>
        <div class="skinleftpanebox">
            <div class="leftpane" id="LeftPane" runat="server"></div>
        </div>
    </div>
    <div class="contentWrap">
        <div id="ContentPane" class="ContentPane dnnpane" runat="server" visible="false"></div>
    </div>
</div>
 

------------ CSS file ---------------

 @charset "utf-8";

.Head{border:none!important; margin:0px!important;}
.ControlPanel .RadComboBox{width:205px!important;}
.ModuleTitle_SubMenu{ z-index:1000!important}
.clear { clear:both; font-size:0px;}
html,body {font-family: Arial, Helvetica, sans-serif;font-size:20px;margin:0px;padding:0px;height:100%;}
html,body,#Body,form,#Form{height:100%;color:#0d15be;}
form{height:100%; margin:0px;}
.Normal, .NormalDisabled{font-family:DistrictPro Thin, Arial, Helvetica, sans-serif;font-size:20px;color:#0d15be;}
#skinall {position: relative;width:100%;min-height:100%;min-width:960px; overflow:hidden;}
.skinleft{float:left; width:385px; position:relative; z-index:9999;}
.skinlogo{padding:32px 0 32px; text-align:center;}
.skinmenu{border:1px solid #000; border-left:none; border-right:none;padding:12px 0; text-align:center;}
.skinleftpanebox{ text-align:center;}
.leftpane .Normal{ text-align:center;}

.contentWrap{margin-left:385px;}

#skinfoot {position:absolute; bottom:0px; width:100%;vertical-align:baseline;}
/* =S Css link==========*/
.wzdh,.wzdh a:link,.wzdh a:active,.wzdh a:visited{color:#a0a0a0;}
.wzdh a:hover{color:#cb2a15; text-decoration:none;}
/* =S Css link end===*/
/* =S Css end */
img{border:none;}
TH,TD,DIV { vertical-align:top;}
p {margin:0px;}
.lt {text-align:left;vertical-align:top; }
.h {height:100%}
.w{width:100%;}
.wh{width:100%; height:100%;}
td{white-space:normal;}

/* Event Viewer Css*/
 span.Normal{color:#000!important;}
.GeneralAdminOperation .Normal{color:#fff!important;}
.OperationSuccess .Normal{color:#fff!important;}
.OperationFailure .Normal{color:#fff!important;}
.HostAlert .Normal{color:#fff!important;}
.ItemDeleted .Normal{color:#fff!important;}
.ItemCreated .Normal{color:#fff!important;}
.Exception .Normal{color:#fff!important;}
/*===END===*/
.Head                    {font-size:11px; color:#000; font-weight:bold}
.SubHead                {font-size:11px; color:#000;}
.SubSubHead                {font-size:11px; color:#ddc893;}
.NormalBold             {color:#06f;}

.ControlPanel .CommandButton,.ControlPanel A.CommandButton:link,.ControlPanel A.CommandButton:visited,.ControlPanel A.CommandButton:active    {color:#000;TEXT-DECORATION:none}
.ControlPanel A.CommandButton:hover    {color:#b9820d;TEXT-DECORATION:underline}
.CommandButton,A.CommandButton:link,A.CommandButton:visited,A.CommandButton:active{color:#b9820d;TEXT-DECORATION:none}
A.CommandButton:hover{color:#cb2a15;TEXT-DECORATION:underline}

A,A:link,A:visited,A:active{color:#cb2a15;text-decoration: none;}
A:hover    {color:#b9820d;TEXT-DECORATION:underline;}
/* =S Skin JDMENU ===================================================== */
ul.jd_menu:after{content:".";display:block;font-size:0px;height:0px;clear:both;}
ul.jd_menu{display:inline-block;}
ul.jd_menu{display:block;}

.jd_menu,.jd_menu ul,.jd_menu li {margin:0;padding:0;list-style:none;}
.jd_menu {padding:0px; text-align:center;}

.jd_menu > li {
    text-align:center;
    display:inline-block;
}
*+html .jd_menu > li {
    display:inline;
}
*+html .jd_menu > li >a {
    display:inline;
}

.jd_menu > li {
    text-align:center;
    padding-left:25px;
    margin-left:7px;
    background:url(images/menu_icon.jpg) no-repeat left center;
}
.jd_menu li a {
    font:18px/43px DistrictPro Thin, Arial, Helvetica, sans-serif;
    display: block;
    color:#0d15be;
    white-space:nowrap;
    cursor:pointer;
    text-decoration: none;
    font-weight:normal;
    text-transform:capitalize;
    padding:0px;
}
.jd_menu > li.activetab,.jd_menu > li.jdm_hover,.jd_menu > li.jdm_active {
    text-decoration:none;
    background:url(images/menu_icon.jpg) no-repeat left center;
}
.jd_menu > li.activetab > a,.jd_menu > li.jdm_hover > a,.jd_menu > li.jdm_active > a {
    color:#0d15be;
    text-decoration:none;
    background:url(images/menu_hover_r.gif) no-repeat right bottom;
}
.jd_menu > li:first-child {
    padding-left:0px;
    margin-left:0px;
    background:none; }
/* =S Sub Menu -------------------------------------------------------- */
.jd_menu ul {
    display:none;
    position:absolute;
    z-index:10000;
    background:#2e3192;
    min-width:145px;
}
.jd_menu ul ul {margin:0px;}
.jd_menu ul li{text-align:left;margin:1px;}
.jd_menu ul li a {
    padding:3px 8px;
    font-family:DistrictPro Thin, Arial, Helvetica, sans-serif;
    font-size:14px;
    line-height:20px;
    color:#fff;
    font-weight:normal;
    text-transform:capitalize;
}
.jd_menu ul li a:hover,.jd_menu ul li.jdm_hover > a {background:#ccc;color:#0d15be;}
/* =S Menu End ------------------------------------------------------------- */
/* =S Skin Pane ------------------------------------------------------- */
.pane-box {width: 100%;}
.pane-box-sub {vertical-align: top;}
.leftshowpane,.leftpane {padding-right: 3px;vertical-align: top;}
.rightshowpane,.rightpane {padding-left: 3px;vertical-align: top;}
.toppane {padding-bottom: 3px;}
.contentpane {vertical-align: top;}
.bottompane {padding-top: 3px;}
.DNNEmptyPane{ width:0px; padding:0px; line-height:0px; height:0px; font-size:0px; margin:0px; visibility:hidden;}
/* =E Skin Pane ------------------------------------------------------- */

background-repeat: no-repeat;
background: url('img.png') no-repeat;
background-size:  100% 100%;

or if you want to maintain aspect ration to some extent

background-size: 100% auto;

You might also look at using the css3 alternates instead of the percentages - it does an aspect ratio scale that fits the smallest axis
-webkit-background-size: cover; 
-moz-background-size: cover; 
-o-background-size: cover; 
background-size: cover;

for older IE browsers you could also try 
 filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='.myBackground.jpg', sizingMethod='scale'); -ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='myBackground.jpg', sizingMethod='scale')"; zoom:1;

In your css -  this should work for all CSS3 compliant browsers but pre IE 9 would break.

Westa