<form target="_blank" name="f1" method="post" action="sub2.php">

 <img style="cursor:pointer;" onClick="b1_onclick()" src="../images/b1.jpg" width="140" height="74">

 </form>

 <script LANGUAGE="javascript">

 <!--

 function b1_onclick(){

     if(confirm("你确定提交?")){

         document.f1.submit();

         return true;

     }else{

         return false;

     }

     }

     //-->

 </script>