How can I export css in my excel with data using DOM by C#.NET?

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.NET3.5

C#

CSS

.NET

HTML

DOM

This is my code. By using this code I can export all the table in excel. But I can not export css class. As a result the color and style is diplaying in webpage do not shown in excel. Can anyone help me by provide a right solution. How can I export the css

Worksheet worksheet1 = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Sheets[1];

var itemset2 = webBrowser1.Document.GetElementById("t2");

string str = "";

int rowCount = itemset2.GetElementsByTagName("tr").Count;
int colCount = itemset2.GetElementsByTagName("tr")[0].GetElementsByTagName("td").Count;

for (var i = 0; i < rowCount; i++)
{
    for (var j = 0; j < colCount; j++)
    {

        str = itemset2.GetElementsByTagName("tr")[i].GetElementsByTagName("td")[j].InnerText;

        worksheet1.Cells[i + 1, j + 1] = str;

    }


}

and this is my html page sample:

<div id="t2" class="tblcss"> 
<table width="100%" cellpadding="0" cellspacing="0">
  <tr id=r1>
    <td>Telephony By Country</td>
    <td>Jan-2013</td>
    <td>Feb-2013</td>
    <td>Mar-2013</td>
  </tr>
  <tr id=r2>
    <td class="tdhighlight">Calls Offered</td>
    <td>33555</td>
    <td>28201</td>
    <td>27563</td>
  </tr>
  <tr id=r3>
    <td class="tdhighlight">Calls Answered</td>
    <td>32042</td>
    <td>27030</td>
    <td>26273</td>
  </tr>
  <tr id=r4> 
</table> </div>