301 Redirect:
A 301 redirect is the most efficient and spider/visitor friendly strategy around for web sites that are hosted on servers running Apache (check with your hosting service if you aren't sure). It's not that hard to implement and it should preserve your search engine rankings for that particular page. If you *have* to change file names or move pages around, it's the safest option.
A 301 redirect is implemented in your .htaccess file.
What is a .htaccess file?
When a visitor/spider requests a web page via any means, your web server checks for a .htaccess file. The .htaccess file contains specific instructions for certain requests, including security, redirection issues and how to handle certain errors.
What is a 301 redirect?
The code "301" is interpreted as "moved permanently". After the code, the URL of the missing or renamed page is noted, followed by a space, then followed by the new location or file name
How do I implement a 301 redirect?
First of all, you'll need to download the .htaccess file in the root directory of where all your web pages are stored. If there is no .htaccess file there, you can create one with Notepad or a similar application. Make sure when you name the file that you remember to put the "." at the beginning of the file name. This file has no tail extension.
If there is a .htaccess file already in existence with lines of code present, be very careful not to change any existing line unless you are familiar with the functions of the file.
Scroll down past all the existing code, leave a line space, then create a new line that follows this example:
redirect 301 /old/old.htm
http://www.you.com/new.htm
It's as easy as that. Save the file, upload it back into your web and test it out by typing in the old address to the page you've changed. You should be instantly and seamlessly transported to the new location.
Notes: Be sure not to add "http://www" to the first part of the statement - just put the path from the top level of your site to the page. Also ensure that you leave a single space between these elements:
redirect 301 (the instruction that the page has moved)
/old/old.htm (the original folder path and file name)
http://www.you.com/new.htm (new path and file name)
Search engine spiders & 301 redirects
The 301 redirect is the safest way to preserve your rankings. On the next spidering, the search engine robot will obey the rule indicated in your .htaccess file. The search engine spider doesn't actually read the .htaccess file, but recognizes the response from the server as valid.
In the next update, the old file name and path *should* be dropped and replaced with the new one. Sometimes you may see alternating old/new file names during the transition period, along with some possible fluctuations in rankings as things settle. Don't panic - this is normal and may take a number of weeks before everything is back to normal; but the bottom line is, any change you make has risks - whether it's altering page text or moving/renaming the page. Search engines run by their own rules and can change those rules at any time.
I hope this helps.