Create NotFound page for 404 error in Sitecore

Create template, layout and content for Notfound page.

Changes in web.config file

<setting name="ItemNotFoundUrl" value="/Notfound.aspx"/>

<setting name="LayoutNotFoundUrl" value="/Notfound.aspx"/>

<setting name="LinkItemNotFoundUrl" value="/Notfound.aspx"/>

<setting name="NoLicenseUrl" value="/Notfound.aspx"/>

In Notfound.aspx page write below code

protected void Page_Load(object sender, EventArgs e)

{

Response.Status = "404 Not Found";

Response.StatusCode = 404;

}