The most popular server errors we’ve met while checking the web for broken links are:

• Request/server exceeded time limit. Surprisingly this is a very common error. Perhaps too many webmsters forgot to optimize their scripts or databases? Seeking into archive too deep? We can’t guess the real problem, but the lesson is check your old pages/scritps if they are still working, can handle the current load, and if your website’s archives are available.
• Can’t connect to SQL – is a very common problem. And this type of errors are fixed very fast, because they are easy to spot since they are affecting almost the whole site.
• Error in SQL query – is a less noticeable message than SQL server errors, but it is easy to fix as well.
• CMS error pages. These are the most informative ones. Developers usually forget to turn off debug messages. These are very dangerous, because they provide so much information for possible hackers.
• Down for scheduled maintenance. Such common and simple pages like this usually show random error numbers like 404, 500 and so on.

Worst solutions to the 5xx error pages

• Trying to show site’s main page. Actually sites like this try to show their main page everywhere: it’s for a 404 page, for any 5xx page, etc. Most of the time this appears as a big mess to a site’s visitor and does not provide any valuable information about what he can do next (if he wants to stay on the same page).
• JavaScript popups with debug messages. Common?!
• Showing return to the original page when the “original page” link points to the same page user is at.

5xx error screenshots we made for you

Clean and simple error page

Internal server error (problem description in Japanese)

Wordpress maintenance mode plugin in action. Website is down for maintenance

AT&T suggests users to return to the original page, but this time button leads visitors to the same page

Talking to aliens? Are BOF or EOF the names of your mothership? And what should your website’s user do now?

Nice looking server error page

Something blew up on digg’s server. One of the shortest error pages we’ve discovered.

Django gives a very detailed (and nice looking) report of what’s happened, but on production sites do not forget to turn that thing off in order not to tease hackers.

Drupal – site is down for maintenance.

Geocities is down. Nice and useful error page from Yahoo. But the title is a bit misleading. Isn’t it?

Server error. Because some of the text is bold red – we guess that something serious has happened.

Sweet and clean. In Russian.

Maxim tries to be funny.

An error happened in mod_python. The big snake is not happy.

MSDN tries to be helpful.

Even social networks go down.

Oh, database is not accessible.

Parallels – internal server error.

jQuery – no such file in repository (why not 404 then?)

Out of operation.

Being helpful and informative.

Ruby fails

Very nice design (actually we see this page for all errors on that site and we love how it looks)

Site offline. Gray color is back into fashion this year.

Oh, so we are the robot? And you are a brick without soul goddammit Gooogle!!!

Look! Robot’s lost its head!

Tomcat broke.

Site is under construction.

Lions!

Something wrong at Yahoo!

XSL file not found.

A “permanent” broken link occurs when a domain name is completely inaccessible or has expired. The domain wasn’t renewed by the webmaster – abandoned only to be bought by spammers who now have the advantage of the site’s former Internet credibility. Other sites that have a link to that domain now have sent their users to the spammer’s site.

Obviously, it’s good practice to know when certain domains expire, especially your own. One of the more popular services is Go Daddy, who will monitor expiry date and domain information for a fee in return. This is good and bad: you might be a responsible and proactive webmaster, who renews in plenty of time, or you could be a spammer waiting to pounce.

If you find a domain inaccessible error, you should look for alternatives or cached content – refer to this LinkAider blog post for more information about how to deal with broken links.

“Temporary” broken links occur when sites go down for maintenance from time to time. Other sites experience network or software errors. In these cases, you’ll probably see a custom error message explaining what has happened. Twitter is the most obvious example of constant downtimes. Its infamous downtime has become the topic of Internet folklore and is a part of many jokes already. Furthermore, Twitter was the inspiration for funny projects like: istwitterdown.com (now defunct itself – how ironic!) August 2009 was rather tough for Twitter according to the chart from the pingdom monitoring service. Growing pains or maintenance can take a toll – but downtime on a social network is not as serious as downtime for your income-generating site. Although these days you may argue that Twitter now provides this type of service and should be making uptime guarantees like other hosting providers.

Hosting providers build contracts around guarantees for uptime. Typically, they are expressed using a percentage. Percentages put a context around the amount of time that a server/hardware/network is continually available (its availability). Percentages make the hosting contract look great at first sight. However, let’s do some math. If a hosting provider says:

• 90% uptime, it means the server may be down 876 hours a year
• 95% = 438 hours down
• 99% = 87 hours, 36 minutes
• 99.9% = 8 hours, 45 minutes, 36 seconds
• 99.99% = 52 minutes, 33.6 seconds
• 99.999% = 5 minutes, 15.36 seconds
• 99.9999% = 31.68 seconds

Of course, these are just network guarantees. Webmasters can also experience some downtime (on top of that) due to script mis-configuration, bad coding or human errors.

Also, when double checking and/or fixing your broken links manually, keep in mind that some websites may be inaccessible within a certain network location or country. So if you have some doubts, check services like these: downforeveryoneorjustme.com and dingitsup.com.

Downforeveryoneorjustme.com is a nice test to do when your users tell you that a site is down. You can check it online and then diagnose the problem – it might be their machine, not the server or the network.

Dingitsup.com sends a text message to let you know when a site is back up or has gone down. Be the first one to know if a site goes down before your end-users or customers start calling. The last thing you want to send out is a large email campaign and have a flood of complaints about a site that is unavailable.

In summary, if you have any doubts about a domain link, double-checking is always the safest route. If you’ve already signed up with LinkAider, you know that you can re-run your broken link report with a single click. If you haven’t signed up yet, consider doing it now. It’s free.