How to open excel doc in aspx page?

Question

how to view the excel document in aspx page using iframe.how to use this one i have used .

 

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" ContentType="application/vnd.ms-excel" %>

 <iframe src="" width="400" height="300" ></iframe>

 

i have used  above code but the excel file is directly downloaded not opened how to do it.