httpwebrequest response omits part of html page source

[lifeform23]

I am writing a program to take stock option data from the Yahoo Finance web site. The page returned using the pagesource function in a browser has all the data in it, but the data returned by VB.NET leaves out the data I am looking for. This used to work and then this problem cropped up.
Any suggestions as to how to resolve this problem would be appreciated.
Here is my code:

Dim Source_code As String = ""
        Try

            Dim request As System.Net.HttpWebRequest = System.Net.HttpWebRequest.Create(web_page_URL)
            Dim response As System.Net.HttpWebResponse = request.GetResponse()

            Dim stream As System.IO.StreamReader = New System.IO.StreamReader(response.GetResponseStream())

            Net.ServicePointManager.UseNagleAlgorithm = False

            Source_code = stream.ReadToEnd() 'gives less content than pagesource in browser