Page Reload After Back Button - Submit Form Twice

[Frawls]

Hi

Can any one give me some help with this problem please?

Here is the scenario:

A user submits page 1 which is a web form.

After the form has been submitted they are (redirected) onto the next
page, page 2.

The user then clicks back on the browser.

They are now back in page 1

If the user clicks the continue button on page 1 this time the page
just reloads and the user has to click submit again to get to page 2.

In other words after clicking the back button the user has to submit
the form twice. (the first time it does not get submitted the page just
reloads)

Is this a known issue? Can anyone tell me what is causing it and how to
rectify or fix it??

Any help would be greatly appreciated.

Here is the c# code for the page load and also the code for the submit
button:

private void Page_Load(objec t sender, System.EventArg s e)
{
if(Session["Complete"] == null || Session["Complete"].ToString()
!="complete")
{
Response.Redire ct(NormUrl);
}

if(!Page.IsPost Back)
{

bttnContinue.Im ageUrl = "Images/Bttn_Continu.gi f";

ctrlAddress.Pop ulateDD();
ctrlAddress.Pop ulateY();
ctrlAddress.Pop ulateM();
ctrlAddress.Pop ulateT();
}
else
{
if(Session["_ViewState "] == null)
{
ctrlAddress.Pop ulateDD();
ctrlAddress.Pop ulateY();
ctrlAddress.Pop ulateM();
ctrlAddress.Pop ulateT();
}
}
}
private void bttnContinue_Cl ick(object sender,
System.Web.UI.I mageClickEventA rgs e)
{
string str1Complete = "complete";

ClearErrors();

ctrlAddress.Rea dFields();
ctrlAddress.Cle arErrors();

bool bOk = ctrlAddress.Val idateFields();
bool bOk1 = ctrlAddress.Val idateAmountYear s();
if(bOk == true && bOk1 == true)
{

ctrlAddress.Cre ateSessionVaria bles();

Session["1Complete"] = str1Complete;

Response.Redire ct("2.aspx");

}

if(bOk == true && bOk1 == false)
{

ctrlAddressDeta ils.CreateSessi onVariables();

Session["1Complete"] = str1Complete;

Response.Redire ct("1a.aspx");

}

else
divOrderError.I nnerHtml = "Blah.";
divOrderError2. InnerHtml = "blah.";

return;
}

[Frawls]

Can anyone please help with this one??? Still very stuck on it... Thanks