[Olggga]

пробую так не работает:

<table>   
     <tr>   
        <td class="sumItg">1</td>  
         <td class="test">2</td>  
        <td class="sumItg">2</td>   
         <td class="test">3</td>  
         <td class="sumItg">3</td>   
         <td class="test">4</td>  
    </tr>   
 </table>   
 <span id="parent"></span>  



<script>

 function nextElementSibling(elem) {  
     if (elem.nextElementSibling) {  
         return elem.nextElementSibling;  
    } else {  
         while (elem.nextSibling) {  
             if (elem.nextSibling.nodeType == 1) {  
                return elem.nextSibling;  
            } else {  
                 elem = elem.nextSibling;  
             }  
         }  
     }  
     return null;  
} 

	 window.onload = function () { 
   var sumItg = 0; 
    var td = document.getElementsByTagName('td'); 
   var i = td.length;  
    while(i--) { 
       if(td[i].className == 'sumItg') {  
             sumItg += +td[i].innerHTML * td[i].nextElementSibling.innerHTML; 
         } 
     } 
     document.getElementById('parent').innerHTML = sumItg; 
 } 
 </script>