Displaying Message Before Redirecting

Hi
i have written the below lines of code in my project .I am not excuting it properly .
{
Page.ClientScript.RegisterStartupScript(typeof(string), "MyScript", "<script>alert('Data Submitted Successfully')</script>");
Responser.Redirect("inbox.aspx");
}
it i wrote like the above it is directly redirecting into inbox.aspx page with out showing message first .Please tell me know what exaclty happening there.

Thanks In Advance..

Mahesh Thandra