Iis 301 ошибка

If it’s asp 2 and above you can implement it in 2 ways:
1) ASP.NET: Redirecting with ASP.NET and IIS
you can implement 301 redirects using ISAPI Rewriting modules, products like UrlRewriter.NET which is discussed in Chapter 3, «Provocative SE-Friendly URLs,» of the book, Professional Search Engine Optimization with ASP.NET: A Developer’s Guide to SEO, or from within your ASP.NET code by setting the appropriate header data.

When using ISAPI_Rewrite, redirecting is implemented similarly to URL rewriting, except that you specify a redirection status code as a parameter.

Example :
The following rule does a 301 redirect to Catalog.aspx when the initial request is for Catalog.html:

301 Redirect Catalog.html to
Catalog.aspx RewriteRule
^/Catalog.html$
http://seoasp/Catalog.aspx [RP]

2) In Code
If you want to implement the redirect yourself, you need to manipulate the response headers using the Response object provided by your current HttpContext object. Here’s how to 301 redirect Catalog.html to Catalog.aspx yourself:
if (context.Request.Path == «/Catalog.html»)
{
context.Response.Status = «301 Moved Permanently»;
context.Response.AddHeader(«Location», «http://www.example.com/Catalog.aspx»);
}
Explanation: The first URL should be a relative path to the old URL and the second one should be an absolute path to the new URL.