Why?

Because I edit the .htaccess by adding these lines as follow…

Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^example\.com
RewriteRule ^(.*)$ http://www.example.com/$1 [R=permanent,L]

(where example is substituted by a domain name of your choice)

Usually this should work fine in ordinary sites.

BUT NOT FOR WORDPRESS.

With these modifications, all my non-www links redirect to HOMEPAGE, and they are considered as 404 error!

And with this setting in another domain of my own, all pages are perceived as duplicate content. Horrible.

It is even worse than doing nothing.

So how do I fix it?

Use this Permalink Redirect plugin.

Enable redirect to www for all non-www links under setting for the plugin. Certainly, you should enter the domain name with www in general setting. And the htaccess file should be writable.

I feel sorry for all those seeking for solution in my posts from search engines, because they all end up as redirection to homepages. My 404 page is set to redirect to home.

If you use wordpress and wish to have consistent permalink, be sure to get the plugin!