Google webmaster tools says: “We’ve detected that your 404 (file not found) error page returns a status of 200 (Success) in the header.“.
Status codes:
- 200 – The request was fulfilled.
- 404 – The server has not found anything matching the URI given.
Why is this a problem? Well for a normal user with a browser this has no effect what so ever, but from a search engines perspective if you return status 200 instead of 404 you are basically saying: “yes, this page exists and you can index it” while in fact it does not exist and it should not be indexed.
How to fix this in asp.net:
You can use:
<% Response.Status = "404 Not Found" %>
or from code behind:
protected void Page_Load(object sender, EventArgs e)
{
Response.Status = "404 Not Found";
}