HTML table creation with smooth lines

I need to create a table like below.(lines are very smooth)All these need to create using html because it uses in .cs file using StringBuilder.for the last row i have crated sepeate table & row for that.because it’s only a 1 row(for that i have tried it with colspan but no luck)

I have tried like below.

String _tableHeaders = “<table style =’height:auto;text-align:center;border:1px solid #525151;width:100 %’><tbody>” +
“<tr style=’width:100%’;border:solid #525151 1px’>” +
“<th style=’width:2%;border:solid #525151 1px;’></th>” +
“<th style=’width:8%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;’>test1</th>” +
“<th style=’width:2%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;’>test2</th >” +
//some rows removed
“<th style=’width:10%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;’>test8</th>” +
“</tr>”;

foreach (var news in newsDetails)
{
_tableHeaders = _tableHeaders + “<tr style =’width:100%;border:solid #525151 1px;’>”;
_tableHeaders = _tableHeaders + “<td style=’width:2%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;font-size:12px;’>” + “test” + “</td>”;
_tableHeaders = _tableHeaders + “<td style=’width:8%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;font-size:12px;’>” + “test” + “</td>”;
_tableHeaders = _tableHeaders + “<td style=’width:2%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;font-size:12px;’>” + “test” + “</td>”;
//some rows removed
_tableHeaders = _tableHeaders + “<td style=’width:10%;border:solid #525151 1px;font-family:Arial,Helvetica,sans-serif;text-align:left;font-size:12px;’>” + “test” + “</td>”;
_tableHeaders = _tableHeaders + “</tr>”;

}
//for the whole row i have crated a table again with 1 row.
_tableHeaders = _tableHeaders + “<table style =’height:auto;text-align:center;border:1px solid #525151;width:100%’><tbody>”;
_tableHeaders = _tableHeaders + “<tr style=’width:100%’ id=’tblDetail’>”;
//some <td> columns removed.
_tableHeaders = _tableHeaders + “</tbody>”;
_tableHeaders = _tableHeaders + “</table>”;