Check for the number of rows found in the query result ..
if(mysql_num_rows($res)<1){
// no results found
echo "<a href='newpartshort.php?orderno=$ono&part=$part&qpid=$qpid&board=$board&subject=$subject&StudentId=$S tudentId&totalrows=$totalRows1'><img src='img/not_answered.png'></a>";
}