How is auto-redirecting done?

There are a number of ways of redirecting. Here are the two main ones:-
The Meta Refresh Tag
<meta http-equiv="refresh" content="5;url=http://domain.com/page.htm">
This tag, which should be placed in the HEAD section of the redirecting page, tells the browser to refresh the page by loading the stated URL. The "5" tells the browser to do it 5 seconds after loading.
Nobody is against this method as long as the number of seconds delay is sufficient for the surfer to see the page and to be able to read some of it. A typical use is after posting a message in a forum where the poster is given a confirmation page that, after a few seconds, automatically returns to the forum.
However, some people question this method when the delay is set to 0 (immediate) or a tiny number of seconds. I have shown that there is nothing whatsoever wrong with an immediate redirect. I have shown that search engines are happy to do it, and I have shown that people want to go to what the link text tells them is at the other end - without any delays. There are valid reasons to set the delay to 0. Setting it higher than 0 and delaying the surfer en-route, for the sake of making some silly people happy, is just plain stupid.
Javascript Redirect
<script language="javascript"><!--
location.href="url"
//-->
</script>
where url is the full or relative URL of the page to redirect to.
Better still is the following script:-
<script language="javascript"><!--
location.replace("url")
//-->
</script>
In this case, the redirecting page is not retained in the browser's History, and the Back button goes to the page before the redirecting page, thereby avoiding that awful trap where clicking the Back button takes you back to a redirecting page, which immediately redirects you forward again to the page you want to leave.
The above is a typical example of an immediate redirect to the specified URL. If the script is placed in the HEAD section at the top of the page, the redirection occurs straight away, otherwise it may take a short time for the page to render before the browser even realizes that the script exists.
If required, the script can be stored in an external file and loaded by the following line, where "filename.js" is the path and name of the external file:-
<script language="JavaScript" src="filename.js"></script>

Summary
I have demonstrated that there is nothing wrong or unethical with the auto-redirecting method as used in search engine optimization, provided that the final destination contains what the surfer expected to see. But the main cause of complaint about the method is when an auto-redirecting doorway page is listed in the search engine results. That's what I'll come to next.