3) A search Box
If they know what they were looking for but they just can’t find the exact page or its address the having a search box would be very handy here. There are plenty of free tools out there that can help you integrate a search function feature into your website. Even Google is offering it which you can get it for free and customize it for your own website.
It’s called Google Site Search and it you can get it at //www.google.com/sitesearch
Or if you have a new visitor to your site and he/she doesn’t know what to search for in the first place? Still not a problem, have a link to your sitemap ready and on display included into your custom error 404 pages. That way, your visitor can browse through and click on other links of interest. This is the perfect excuse to spruce up your sitemap page to make it more navigation-friendly and easy on the eyes. Having a page mess-full of jumbled up links is just as bad as having none at all.
5) Back to Square One
The main page or home page is usually one of the most visited page of any website. So have it’s best to include a link on your error 404 pages which can usher them back to the main page as it might be the page they intended to go in the very first place.
6) Slip It In
Since you already have a website visitor landing on your 404 page, why not have a display of your business’ main product/service on the page as well? Chances are it is something they were looking for when they paid a visit to your site. While customizing your error 404 pages is great practice when it comes to website design some people make the mistake of going overboard with their 404 pages. They usually include in too many trivial links and information which should not belong on an error 404 pages. A custom error 404 pages is meant to be a means of getting visitors back on track and not to replace the missing or unavailable page.