The Specialty Pages tab holds configuration settings for all of the various Wordpress pages that you cannot directly edit. This includes the archives, search, and 404 pages.
Like all other pages / posts you can choose a custom sidebar and a sidebar layout for each page. Depending on your theme you can also upload an image to use as the background.
The Wordpress archives is like a big catalog of all your posts. This page will be displayed when a user is viewing a date link, tag link, category, author, etc etc. An example archive link would be something like this,
That will bring up the archives page and display all posts created by the user admin.
Another example would be if you want to view all of your posts that are not assigned to a category,
The search page is displayed anytime you put a search term in the URL. It's just like the archives but your actually searching for terms in your post content. An example search link would look like this,
If you use the search widget or our search shortcode you can see how the URL changes to display the search page after you type in some terms and hit enter.
The 404 page is displayed anytime someone visits a link that Wordpress cannot identify. The most common reason why this would happen is if someone links to your page and over time you decide to delete the page or post. Now anyone visiting that link will be redirected to the 404 page because Wordpress cannot find it.
You can view the 404 page by typing in something like this,
If you decide you want to change the 404 text to something else you can find this area in /wp-content/themes/[your_theme]/lib/functions/theme.php around line 2360.