1. Retry the web page by pressing F5, clicking/tapping the refresh/reload button, or trying the URL from the address bar again.
The 404 Not Found error might appear for several reasons even though no real issue exists, so sometimes a simple refresh will often load the page you were looking for.
2. Check for errors in the URL. Often times this error appears because the URL was typed wrong or the link that was selected points to the wrong URL.
3. Move up one directory level at a time in the URL until you find something.
If you have moved all the way up to the website's home page, try to run a search for the information you're looking for. If the site doesn't have a search function, try navigating to the page you want using category links to dig deeper into the site.
4. Search for the page from a popular search engine. It's possible that you simply have the entirely wrong URL in which case a quick Google or Bing search should get you where you want to go.
If you do find the page you were after, update your bookmark or favorite to avoid the HTTP 404 error in the future.
5. Clear your browser's cache if you have any indication that the 404 message might just be yours. For example, if you can reach the URL from your phone but not from your tablet, clearing the cache on your tablet's browser might help.
You might also consider clearing your browser's cookies or at least the one(s) involved with the website in question if clearing the cache didn't work.
6. Change the DNS servers used by your computer, but usually only if an entire website is giving you a 404 error, especially if the website is available to those on other networks (e.g., your mobile phone network or a friend in another city).
404s on an entire website isn't particularly common unless your ISP or government filters/censors websites. No matter the reason, if it does happen, giving another set of DNS servers a try is a good step to take. See our Free and Public DNS Servers List for some alternatives and instructions on doing this.
7. Contact the website directly. If they've removed the page you're after then the 404 error is completely legitimate and they should be able to tell you that. If they've moved the page and are generating errors instead of redirecting visitors to the new page, they'll be happy to hear from you so they can go fix it.
If you suspect that everyone is getting a 404 error for this site, but you're not sure, a quick check on Twitter might help clear it up. All you have to do is search Twitter for #websitedown, as in #facebookdown or #youtubedown. Twitter users are usually the first to start talking about a website outage. Learn how to tell if a website is down for everyone or just you for some more help.
8. Finally, if all else fails, wait. No, it's not fun, but it might be your only course of action, especially if you're confident the 404 error shouldn't be happening (i.e., the page really should be at the URL you have and others are having the same problem and find it equally strange).