[MikhailGirshberg]

Скрипт напишем так:

function c_r(addr){
   if(confirm("Do you really want to delete this entry?")){
    var form = this.parentNode
    form.action = addr
    form.submit()
   }
}

HTML - так:

<form method="POST">
  <input type="hidden" name="del_id" value="id_чаво_удалять"/>
  <input type="button" value="Delete" onclick="c_r('куда переходить')"/>
</form>