The importance of 404 pages
A 404 page is something which is actually very important to a website. Depending on how old your website is and a number of other factors you can inevitably find yourself removing old pages and in turn you want users who arrive on these old pages to have a clear message about what has happened to them. A 404 page at its heart is simply a message to tell users they have clicked a link that leads to nothing. This link can be a product of poor coding, a mistyped URL on the users part, or as stated before can lead to pages which no longer exists. Because a 404 page is not technically a page, but merely a message to the user it must be short and concise and communicate to the user that although the content they are looking for may not exists, there is another way to find it. A search box for your website is usually one of the best things you can place on a 404 page. It gives users a simple way to search through your website and keeps them within your site structure. Although on a 404 page you could just have a simple link to your home page or similar you don’t want something too basic on the page, you want to give users some flexibility to find something that could be quite specific or hard to find.
Build the perfect 404 page
Because a 404 page should be of limited text content it does give you a lot of scope to experiment with visuals on your 404 page. Nothing is less appealing than clicking a broken link and landing on a boring 404 page with no visuals and just a link to your home page, or the opposite, landing on a 404 page with paragraph upon paragraph of boring pointless text. A much better experience is when you click a broken link and land on a 404 page that gives a short and concise message with a search facility and is accompanied with unique visuals that communicate a bit about the site. You don’t even have to communicate through text content that the user has landed on a 404 page but you can do it entirely though your visuals which most of the time is a better option. Always keep in mind that users can drop off your website very easily when they click broken links through frustration with not being able to find the content they want. A 404 page is the chance to say “you clicked a broken link but maybe this content will help or maybe you can find it this way”.
A 404 page should return a 404 header to search engines when the link they are following does not generate content. If your 404 page isn’t returning a 404 header then you have a big problem. A 404 page must return a 404 header or else you can end up with a lot of duplicate content and soft 404 errors. Your only real concern should be when you are building a dynamic site and you are including a 404 template file. Make sure you set a 404 header and kill your script if needs be.
Using 404 pages for SEO
404 pages are incredibly important for SEO. They are your best tool to stop dynamically generated pages causing you problems. When URL parameters are used to generate content you should make sure when no content is returned and a proper 404 header and page is returned otherwise you can end up with a large number of soft 404 errors within your site. If you want to get an idea of just how many strange URL’s can be returned from dynamically generated pages make sure you have Google Analytics tracking code within your 404 page. You can then view in Google Analytics the list of URL’s that led users to your 404 page. Analyse what is returned carefully and you can probably figure out any errors with your URL's that are not returning a 404 when they should be.