If a user has a bookmark for <a href="http:&#x2F;&#x2F;a.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;a.com&#x2F;</a>, and the ISP redirects with a 301 Permanent Redirect to <a href="http:&#x2F;&#x2F;isp.net&#x2F;" rel="nofollow">http:&#x2F;&#x2F;isp.net&#x2F;</a>, the browser will rewrite a.com to isp.net.