Microsoft has released a WordPress plugin named Bing404 to showcase relevant links on the 404 page of WordPress blogs. The traditional way of showing 404 message is that “The page you are looking for is not available” but this plugin will show some links related to the content the visitor is looking for. You can customize the plugin to show links and suggestions from your site only or it will use Bing Search to show content from web.
Most of the professional bloggers has already redesigned their 404 pages to show latest posts or popular posts from their site but this kind of suggestion will definitely help them to increase the page views and traffic.
Here is the description mentioned on Bing404 Plugin page,
Using the Bing Search library, this plugin will intercept your standard 404 page and return a list of urls that may help your user find the content they are looking for. You can limit the search to just the content on your site, set a default search in case the computed one doesn’t return any results, and set a host of other options, all designed to provide your users with quality recommendations.
BIng404 is having option to customize the look and feel of the 404 page. So if you are using Google Custom Search on 404 page to provide an option for search and for your monetization then you can add Google Custom Search on the template file to get that as well. As the links generated out of Bing404 will be dynamic, it will not affect your Google Page Rank and SEO. So if you are using WordPress as blogging platform, then you can try Bing404 on your self hosted blog and customize 404 page to provide some suggestion and relevant content to your viewers.