The MDC wikis have the ability to redirect to external websites. We have done this so we can have links to external pages within the wiki that will be included in the wiki category pages.
Creating an external redirect
To create one of these external redirects, do the following:
First, create the page that will be the external redirect, suffixing the title with "(external)". For example: Mozilla Project Wiki (external). This "(external)" suffix is used as an indicator to the user that the link he/she is about to click will take them to a page outside of the wiki. This is primarily for use in the Category lists, where manual linking isn't possible. See below for more information about creating manual links to External Redirect pages.
Next, edit that page and add the redirect command, followed by the desired target URL enclosed in double square brackets. For example:
#REDIRECT [[http://wiki.mozilla.org]]
Finally, add a category to the redirect page. Note that the category must be on the same line as the REDIRECT command, or the parser will ignore it. For example:
#REDIRECT [[http://wiki.mozilla.org]] [[Category:Mozilla Project:Other Resources]]
When this is finished, simply save the page as normal.
Manually linking to external redirects
You should not create links to external redirects. Instead, just create regular external links to the site. The reason for this is because linking to an external redirect obscures the URL and users won't know where they will end up. This can be pretty annoying, and annoying users is a bad thing.
Editing External Redirects
Since an external redirect page immediately bounces you to the external site, editing the external redirect can be a challenge. To do so, simply add "?action=edit" to the end of the URL for the external redirect page. This is somewhat inconvenient, but it works. For example:
Migrating pages referred to by external redirects
If you migrate an article into the MDC check the category page to see if there's an external redirect pointing at it as well.
If there is, check the "what links here" (link in right column, in Toolbox) to see if any other pages link to that external redirect. If any links exist, change them so they point at the newly migrated article.
When no pages link to the external redirect page, redirect it to the newly migrated article and add the "Junk" tag to the article so our helper gnomes know to delete the page.
If you have any questions about using External Redirects, feel free to email Eric Shepherd.