301 redirection
301 redirection is an apache statement which redirects a users request for a web page to another page. For example let's say you you have a page called 'blog.html' and you wish to rename the page 'web-development-blog.html'. This causes a couple problems.
Basically the problem comes down to search engines such as google and how it stores information about your pages. The major issue is search engines don't update their information quickly, your old address could be stored in google's results for a week or two, which results in users coming to your website and not finding the appropriate page.
The second issue is once google finds the new page that you created, it may believe it is a new page and you will lose all your rankings that your previous page had. I personally don't believe this is the case and believe google's algorithms can work out that the new page is a replacement for the old. I personally believe google is very forgiving for changes such as this as their are billions of websites around the world and google understands that most of the websites are not developed well, therefore forgiving algorithms are created giving everyone a fair go. But I can never be sure about this and other search engines may not have this functionality.
Despite all this, a redirection is needed and a 301 redirection is what you need. A 301 redirection says 'this page is not here anymore, here is the new address.
redirect 301 /blog.html http://www.marcwatts.com.au/web-development-blog.html
You may use as many of these as required.