I am trying to create a spreadsheet from mysql data. I have the
requisite headers in place for content type and all that.
All I am doing is executing the SQL query and displaying the data
formatted in an HTML table.

Whatever width I assign to the HTML table columns ( using <td
width="nnn"> it doesn't have any impact on the width of the
spreadsheet column- that is always staying the same.

Any idea how to control it?

The headers I am using are as follows
header("Content-type: application/vnd.ms-excel");
header("Content-disposition: attachment; filename=report.xls");
header("Pragma: no-cache");
header("Expires: 0");