Over the course of time a WordPress blog or site author is bound to change the content of their site and eventually move or even delete and re-write content. This can cause problems with search bots that have previously crawled and indexed your links. If the moved or deleted links can't be found, you might even lose page ranking.
To remedy this we can utilize the 301 re-direct rule to point the old path to the new location. The easiest way to do this is via the .htaccess file.
1. Access your blog directory via FTP
2. Locate and copy the .htaccess file to your computer
3. Open the .htaccess file using a text editor ( I recommend Crimson it's free)
4. Under the line # END WordPress add the following code (changing the paths as necessary):
redirect 301 /oldpath http://www.yoursite.com/newpath/
You can add copies of this line as necessary for each path you would like to redirect
How it works:
The first section of the code redirect 301 /oldpath signifies the path that no longer exisits. In this example the path that no longer exists is /oldpath. Note that your server treats this path "relative to root" as http://yoursite.com/oldpath
You can also redirect an old .html or .php file by adding the extension. For example: /oldpath.html
The second section of the code http://www.yoursite.com/newpath/ tells the server where to route the old path. This new path must be a full URL to the new location… but note that it can link to any website.