Double line in HTML table

[lektion]

I create HTML table in Qt:\[code\]QString css;css = "<style type=\"text/css\">";css += "table.tbl {border-width: 1px;border-style: solid;border-color: black;margin-top: 0px;margin-bottom: 0px;color: black;}";css += "table.tbl td {padding: 3px;}";css += "table.tbl th {padding: 3px;}";css+="</style>";QString text;text="<table width=\"100%\" cellspacing=\"0\" class=\"tbl\">";text+=("<tr><th>1</th><th colspan=\"2\">2</th><th>3</th><th></th></tr>");text+=("<tr><td>1</td><td>2</td><td>3</td></tr>");text+=("<tr><td colspan=\"2\">4</td><td>5</td><td>6</td></tr>");text+=("<tr><td>7</td><td>8</td><td>9</td></tr>");text+=("<tr><td>7</td><td>8</td><td>9</td></tr>");text+=("<tr><td>7</td><td>8</td><td>9</td><td>8</td><td>9</td></tr>");text+=("<tr><td>7</td><td>8</td><td>9</td></tr>");text+=("<tr><td>7</td><td>8</td><td>9</td></tr>");text+=("<tr><td>10</td><td>11</td><td>12</td></tr></table>");\[/code\]And then I printed as a pdf document:\[code\]QPrinter printer;printer.setOrientation(QPrinter::Landscape);printer.setPageMargins(10,10,10,50,QPrinter::Millimeter);QTextDocument *document=new QTextDocument();document->setHtml(css+text);QPrintDialog *dlg = new QPrintDialog(&printer, this);if (dlg->exec() != QDialog::Accepted) return;document->print(&printer);\[/code\]My table have single border but there is double line between third and fourth columns? How can I get rid of that?I can not use image tag because of my reputation but image of my table is here: http://imgur.com/KW3pZEfSorry for my poor English.