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>