Autofit table header width in Flexigrid

Im using the Jquery Plugin Flexigrid as datagrid in my web app. How can I autofit the width of my table header using FlexiGrid? If you dont specify a width to the tag <th> the width of the <td> table will开发者_运维技巧 be different from the width of <th> and the header will be displaced from the rest of the table.