I wouldn’t believe it if it didn’t happen to my sites – a few sites. In the last two months, I noticed Google didn’t crawl my sites daily like before, the pages got de-indexed quickly, the rankings also dropped to nowhere. I thought it was caused by the changes of Google’s ranking algorithm and didn’t look into it. Today, I found an index page wasn’t cached by Google, I feel something is really wrong here.
After some checking, I found it was caused by the links pointing to the non-www verson. This topic has been discussed a lot on the webmaster forums, but I didn’t get it without examples. I didn’t believe Google had such a silly problem either.
Use this blog as an example, it can be accessed with http://www.seoblog.us/ or http://seoblog.us/. I always promote my sites with www version. But if someone links to this blog with http://seoblog.us/, Google treats seoblog.us and www.seoblog.us as two different sites and will dump out www.selbog.us because of duplicated content. Very hard to believe? It’s that that simple, that silly.
As now, I have at least 5 sites ( around one year old) which lost the most pages including their index pages. Since the majority links point to www version, the non-www version has very poor ranking. I can’t find the links pointing to non-www version, I guess they are only a few, I can’t understand why Google dumps out the www version which has hundreds of links. This is the worst thing happened to my websites since I was a webmaster, I have to say it is the silliest thing about the search engines I have ever heard.
You can read more details about this problem here, also many discussions.
This problem can be fixed by redirecting one url to the other one. I used .htaccess, httpd.conf would be better if you have access to the main Apache configuration file, but I didn’t find the page before I made the changes.
Solution
1. Create a text file named “.htaccess” with the following content, place it under the root directory.
RewriteEngine On
RewriteCond %{HTTP_HOST} ^seoblog.us
RewriteRule (.*) http://www.seoblog.us/$1 [R=301,L]
If you have .htaccess under sub-directories, it should be modified accordingly.
RewriteEngine On
RewriteCond %{HTTP_HOST} ^seoblog.us
RewriteRule (.*) http://www.seoblog.us/forums/$1 [R=301,L]
Sub-domains are like this:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.forums.seoblog.us
RewriteRule (.*) http://forums.seoblog.us/$1 [R=301,L]
I also checked some old sites including my two-year-old domain, they don’t have this problem. But if you check the cache of the non-www version, it says it’s a cache of the www version. This problem has been existing for years, Google seemed to fix it some time ago or for some domains, but now it got worse. I don’t know if my sites can be recovered and how long it takes. Keep my fingers crossed 
.