Its clear from the code man. Where ever you are redirecting the user to different page as-
Response.Redirect("default.html");
put this in try block as
try
{
Response.Redirect("default.html");
}
and put a catch block to handle that as -
catch
{
response.redirect("err.aspx");
}
you can see the full code in previous post. the page u r redirecting is
default.html.
Mark as answer if this post helps you.
Hope it helps.
-Manas