This post tells you how to update links across an entire blog at once.
Here's the scenario, you decide to change your domain name and you have 500 posts. You export your content to the new domain, but none of the links update.
Now, you're faced with going through and changing each link one at a time. Don't do it… I've found the solution in a plugin that works great and is available FREE!
That plugin “search and replace”, a simple name that describes exactly what it does. In a matter of minutes you can change every link in every post and page of your blog.
Let's say you don't want to change a URL, but a keyword or some other word or phrase. Just select specific fields in the settings section of the “search and replace” plugin for WordPress.
Find “search and replace” by logging into your WordPress control panel, clicking on “plugins” and then select “add”. Search the WordPress Plugins database for the term, “search and replace” and then install the plugin.
You're ready to go!