Redirect to a new page, when we get 404.htm error page in the application

Create a custom Page Not Found is to create a site level feature receiver that will attach it to the webApplication instance.

On the activated event you would attach it like this:

    [SharePointPermission(SecurityAction.LinkDemand, ObjectModel = true)]
    public override void FeatureActivated(SPFeatureReceiverProperties properties)
    {
      if (properties != null)
      {
        try
        {
          SPSite site = properties.Feature.Parent as SPSite;
          System.Uri webApplicationUri = new Uri(site.Url);
          SPWebApplication webApplication = SPWebApplication.Lookup(webApplicationUri);
          if (webApplication != null)
            webApplication.FileNotFoundPage = "CustomError.html";
        }
        catch (Exception ex)
        {
         throw;
        }
      }
   }

And in your deactivated event you could unattach it by setting the same webApplication.FileNotFoundPage to null.

You will also have to save your Custom Page Not found page in the Layout.

You might also like:

• Connecting Custom Webparts in Moss 2007
• SharePoint 2007 (MOSS/WSS) – Creating an ItemUpdating Event Handler as a feature and Packaging it in .wsp
• Sharepoint Template ID Event Handlers
• Sharepoint Programming interview Questions with Answers Part 2
• create a custom content type in MOSS 2007