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4.2 Auto-Redirecting

Auto-Redirecting is the technique of automatically sending surfers to a different page. It means that just after a page is loaded in the user's browser, he is redirected to a new page.
This technique may be used to redirect people when there is a browser-specific page versions or when a domain has moved. Since these are legitimate reasons, search engines do not punish every kind of auto-redirecting but they try to spot misuse of it. In particular when a user arrives to a website with a content he is interested in, and he is redirected to another website on an entirely different topic.
There are four main methods to redirect a user.

"301 redirect" is the most efficient and Search Engine Friendly method for webpage redirection. It is interpreted like "moved permanently". It is implemented in different way according to the platform.
For instance, if you are using an IIS server, you have to use the internet services manager. After a right click on the file or folder you wish to redirect, select the radio titled "a redirection to a URL"; once entered the redirection page, check "The exact URL entered above" and the "A permanent redirection for this resource". Finally click on 'Apply'.
"301 redirect" allows redirecting all the files and directories of an old website to a new location. Add the following lines of code to the .htacess file, present in the root of the old website.
Options +FollowSymLinks
RewriteEngine on
RewriteRule (.*) http://www.newLocation.com/$1 [R=301,L]
And if you need to ensure that all the request to the address "http://myDomain.com/" will be redirected to the address "http://www.myDomain.com/" you just to add this code to the .htaccess file:
Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^ myDomain.com [nc]
rewriterule ^(.*)$ http://www.myDomain.com/$1 [r=301,nc]

A second way to redirect a user toward a new page, is using a Meta Refresh tag. It has to be placed in the <head> section, it can be detected by the search engines and it is allowed as long as there is a reasonable delay, usually five seconds, between landing on a page and being redirected from it.
The code looks like:
<meta http-equiv="refresh" content="5;url=destinationPage.html">
The content parameter contains the seconds of delay and the destination page, separated by a semicolon. Since it is annoying for the user waiting some seconds, you may think to set the delay to 0 but unfortunately search engines can read HTML and website were penalised for that.
To redirect in a faster way, you may use a JavaScript. Use the code:
<script language="javascript">
<!--
location.replace("destinationPage.html")
//-->
</script>

Using the "replace" function instead of the "href" one, causes the new page to replace the current page in the history of the browser. If a visitor clicks the Back button he will go directly to the page before the redirecting page. It avoids the annoying trap of going back to a page which immediately redirects you to the current page.

Finally you can use a form. A crawler cannon fill any forms, thus it ignores them. But if you use a JavaScript which submits a form as soon as the page is loaded, the user will be redirect to the page which is in the "action" parameter. Here the code:
<head>
<script language="javascript">
<!--
document.myform.submit();
//-->
</script>
</head>
<body>
<form name="myform" action="destinationPage.html" method="get"></form>
</body>

The destination page can be any absolute or relative URL.

It is not auto-redirecting when the server does the entire job, directing two different addresses to the same page. For example, it may happen that you have more possible addresses for the same home page:
http://www.mydomain.com/index.html
http://mydomain.com/
http://www.mydomain.com/
Anyway this is not good from a SEO point of view. If some search engine can handle this situation, Yahoo and MSN for instance, for others, like Google, it causes the so called "Canonical Issues". In fact Google flags the different copies as duplicate content, and penalizes them. Otherwise, it may happen that the different versions are not penalised but the PageRank is split among them so that the overall rank of your homepage will be lower that it should be. At the moment, standardizing the URL of the home page is the only way to ensure that the PageRank is not shared with ghost URLs.