//add a new row to the table
   function addRow()
   {
    //add a row to the rows collection and get a reference to the newly added row
    var newRow = document.all("tblGrid").insertRow();
    
    //add 3 cells (<td>) to the new row and set the innerHTML to contain text boxes
    
    var oCell = newRow.insertCell();
    oCell.innerHTML = "<input type='text' name='t1'>";
    
    oCell = newRow.insertCell();
    oCell.innerHTML = "<input type='text' name='t2'>";
    
    oCell = newRow.insertCell();
    oCell.innerHTML = "<input type='text' name='t3'>  <input type='button' value='Delete' onclick='removeRow(this);'/>";   
   }
   
   //deletes the specified row from the table
   function removeRow(src)
   {
    /* src refers to the input button that was clicked. 
       to get a reference to the containing <tr> element,
       get the parent of the parent (in this case <tr>)
    */   
    var oRow = src.parentElement.parentElement;  
    
    //once the row reference is obtained, delete it passing in its rowIndex   
    document.all("tblGrid").deleteRow(oRow.rowIndex);  

   }

原文: http://www.codeproject.com/KB/scripting/DHTMLGrid.aspx
Dynamically add and remove rows in a HTML table By eeraj