'headers' specifies a list of 'th' elements
<HTML> <BODY> <table width="450"> <tr> <th id="hdr1">Item Number</th> <th id="hdr2">Item Name</th> <th id="hdr3">Item Description</th> </tr> <tr> <td headers="hdr2">cell</td> <td headers="hdr1">cell</td> <td headers="hdr3">cell</td> </tr> </table> </BODY> </HTML>