Kelly,

Just found something else in the source for your page:

You have several tables and <td>s that are wider than the #mainWrapper.

Code:
<!--bof-header logo and navigation display-->
<table width="100%" height="874"  border="0" cellpadding="0" cellspacing="0">
  <tr>
    <td  width="50%" height="874"><img src="images/spacer.gif" width="1" height="1"></td>

    <td valign="top" height="874">
    <table width="800" border="0" align="center" cellpadding="0" cellspacing="0" height="693">
      <tr>
        <td height="151" valign="top" background="images/margo-whbg.jpg">
        <table width="800" border="0" cellspacing="0" cellpadding="0" height="150">
            <tr>
              <td height="150" background="images/margo-whbg.jpg" width="800" valign="top">
  <img border="0" src="images/margotopperopt3.jpg" width="800" height="150"></td>
            </tr>

            <tr>
              <td height="20" background="images/green-block.jpg" width="800" valign="top"></td>
            </tr>
            </table></td>
      </tr>
      <tr>
        <td height="575" valign="top">
        <table width="800" height="594" border="0" cellpadding="0" cellspacing="0" background="images/margo-whbg.jpg" style="border-collapse: collapse" bordercolor="#111111">
            <tr>

              <td height="30" valign="top" style="padding-top:7px ">
              <table width="800" border="0" cellspacing="0" cellpadding="0" height="1" class="text_1" style="border-collapse: collapse" bordercolor="#111111">
                  <tr>
                    <td width="40" valign="top" height="1">
                    </td>
                    <td width="90" valign="top" height="1">
                  <a href="http://www.kellyscountrycorner.com">
                  <img src="images/home-button.jpg" width="90" height="30" border="0"></a></td>
                    <td width="20" valign="top" height="1"></td>

                    <td width="90" valign="top" height="1">
                    <a href="http://www.kellyscountrycorner.com/shop/index.php">
                    <img src="images/enter-button.jpg" border="0" width="90" height="30"></a></td>
                    <td width="20" valign="top" height="1"></td>
                    <td width="85" valign="top" height="1">
                    <a href="http://www.kellyscountrycorner.com/privacy-policy.html">
                    <img src="images/privacy-button.jpg" border="0" width="90" height="30"></a></td>
                    <td width="20" valign="top" height="1"></td>
                    <td width="82" valign="top" height="1">

                    <a href="http://www.kellyscountrycorner.com/about-us.html">
                    <img src="images/about-button.jpg" border="0" width="90" height="30"></a></td>
                    <td width="20" valign="top" height="1"></td>
                    <td valign="top" height="1" width="90">
                    <a href="http://www.kellyscountrycorner.com/sitemap.html">
                    <img src="images/partner-button.jpg" border="0" width="90" height="30"></a></td>
                    <td valign="top" height="1" width="20"></td>
                    <td valign="top" height="1" width="90">
                    <a href="http://www.kellyscountrycorner.com/shop/index.php?main_page=contact_us">

                    <img border="0" src="images/contact-button.jpg" width="90" height="30"></a></td>
                    <td valign="top" height="1" width="40"></td>
                  </tr>
              </table></td>
            </tr>
                <tr>
              <td valign="top" style="padding-top:5px " width="795">
              <img border="0" src="images/berryline.gif" width="400" height="50"><img border="0" src="images/berrylineR.gif" width="393" height="50"></td>
                </tr>

            <tr>
              <td height="511" valign="top">
              <table width="800" border="0" cellspacing="0" cellpadding="0" height="496">
I'd change mainWrapper to match the width of the tables.
Code:
#mainWrapper {
               background-image: url(../images/margo-whbg.jpg);
               text-align: left;
               width: 800px; /* change to match the table width
               margin: 0px auto; /* add auto */
               vertical-align: top;
}
Just a persosnal observation:
I'd junk the tables in the heading and style everything with CSS and the "default" tpl_header.php. As I said just a personal observation.