Nothing sucks on the web like not being able to go to the site you want. Page not found and 404 errors are an inconvenience that entirely halt your workflow. What’s worse than not being able to access a site is not being given relevant information to fix the problem. When users are presented with an error message, they tend to do whatever will make the error go away to get back to their task. Page not found errors can’t be dismissed, because they’re shown instead of the content wanted.

What creates an added level of frustration is not being given information on what the problem is. When users get a Page not found error, they likely have two questions in mind:

  1. Is this problem on my end, or not?
  2. If the problem is on my end, how can I fix it?

These are questions that have been hard for browsers to answer. Currently, Firefox’s network error pages aren’t incredibly useful. They’re certainly not as useful as Chrome’s, which use Google Link Doctor to find possible matches both for subdirectories and domains. That won’t necessarily tell the user if the problem is on their end or not, but it will help if the problem is a typo.

So how could a browser tell users if the problem is on their end or not, without infringing on their privacy? One project that currently takes a stab at this is Herdict, which Johnathan Zittrain’s been working on at Harvard University’s Berkman Center for Internet and Society. What Herdict does is let computer users tell the “herd” – via a Firefox extension – what sites are accessible. The aggregated data can tell if a site is down (because no one can access it), or blocked by a firewall (because only some people can access it), or likely on the user’s end (because everyone else can access it). Not only does that answer the question of “is this problem on my end,” but it may start to answer questions like “is this problem only experienced by my country, network provider, or device?”

Useful stuff! Does it have a place in the browser, and specifically in Firefox? I think that getting and submitting anonymized data should have an increased role in the browser, and especially where it promotes transparency and information to the user. Mitchell Baker has been writing about data, and how Mozilla could be treating aggregated, anonymized data as a public asset that should be freely available. Especially in situations where sites are being blocked and censored, giving users knowledge of the situation seems to align with Mozilla’s goals of transparency and viewing the web as global public resource that must remain open and accessible.

One way something like Herdict could be incorporated is through those Page not found errors. If there were an option on these to submit anonymized data, we could build a pretty accurate view of accessibility information for a website and share it. Allowing users to submit data when there’s a problem is something many programs do already – especially for crashes. This is good design; it makes users feel better by registering the annoyance they feel as a useful data point to developers. Here’s some sketches of what it could look like to incorporate Herdict’s aggregated accessibility data with these error messages:

1. No available information on a site:

2. Site is blocked due to local firewall:

3. Site is down for a country:

4. Site is down for everyone:


One area of Firefox that could use some improvement are the warnings we give when pages are not found.  These could be network errors, firewall issues, URL typos, etc.  Curtis Bartley has been looking at this issue and documenting progress here, and Jesse Ruderman started a bug with some insightful comments here.

Ideally, a good error page does two things:

  1. Tells you what’s wrong in a way that’s both understandable and diagnosable
  2. Helps you decide what to do next

If I type “www.example.cmm” into Firefox now, here’s what I get:


Internet Explorer, Chrome, and Safari all have slight variations on this page.  IE’s isn’t very useful; it gives easy text but no tools. Safari’s design is very minimal, but it does offer search.  Chrome is cutesy, but also intelligently offers suggestions based on what was typed – the most useful of all three.  All three browsers offer additional information via a link, thus removing the bulk of explanation Firefox currently shows.


So what should Firefox do?

For blatant, common URL typos, I think we should redirect straight to the correct URL. currently goes to, why shouldn’t or URLs themselves are an example of forcing users to behave like machines – rather than the preferable reverse – so why not take a step in the right direction by making them more forgiving? (bug freakin’ 175634)

For the addresses that are not blatant typos for existing pages, there’s a few approaches we could take. User-experience-wise, I would love to be able to do better detection of what the problem is and direct the user towards the likely solution. Rather than presenting the user with questions as we do now, we could give them an answer.  We should aim to provide a consistent UI, but perhaps we could change the text sightly based on what the user inputted and try to find the most helpful suggestion. When there’s a very likely solution, that should be the most obvious next step available.

Here’s four scenarios that would cause a 404 today with text customized to what what the user imputed:


While catching all of these scenarios may not be feasible for now, we could be concentrating harder on giving users tools at a 404, not just a warning. I’d love to hear you feedback on this – especially what would help a tech-saavy person such as yourself when you hit a 404.

Just for fun… spoilers!