What might my user have installed thats going to break my web app?

Question

There are probably thousands of applications out there like 'Google Web Accelerator' and all kinds of popup blockers. Then theres header blocking personal firewalls, full site blockers, and paranoid cookie monsters.

Fortunately Web Accelerator is now defunct (I suggest you read the above article - its actually quite funny what issues it caused) but there are so many other plugins and third party apps out there that its impossible to test them all with your app until its out in the wild.

What I'm looking for is advice on the most important things to remember when writing a web-app (whatever technology) with respect to ensuring the user's environment isnt going to break it. Kind of like a checklist.

Whats the craziest thing you've experienced?

PS. I may have linked to net-nanny above, but I'm not trying to make a porn site

Answer 1

Um... browser? ;)

Answer 2

The best advice I can give is to program defensively. For example, don't assume that all of your scripts may be loaded. I've seen cases where AdBlocker Plus will block 1/10 scripts that are included in a page just because it has the word "ad" in the name or path. While you can work around this by renaming the file, it's still good to check that a particular object exists before using it.

The weirdest thing I've seen wasn't so much a browser plugin but a firewall/proxy configuration at a user's workplace. They were using a squid proxy that was trying to remove ads by replacing any image HTTP request that it thought was an ad with a single pixel GIF image. Unfortunately it did this for non-GIF images too so when our iPhone application was expecting a PNG image and got a GIF, it would crash.

Answer 3

Internet Explorer 6. :)

No, but seriously. Firefox plugins like noscript and greasemonkey for one, though those are likely to be a very small minority.

Sometimes the user's environment means a screen reader (or even a braille interface like this). If your layout is in any way critical to the content being delivered as intended, you've got a problem right there.

Web pages break, fact of life; the closer you have been coding and designing up against standards, the less your fault it is.

Answer 4

Something I have checked in the past is loading some of the more popular toolbars that people tend to install (Google, Yahoo, MSN, etc) and seeing how that affects the users experience.

To a certain extent it is difficult to preempt which of the products you mentioned will be used by your users since there are so many. I would say your best bet is to test for the most frequent products that your user base may employ and roll with the punches for the rest. If you have the time to test other possible scenarios, by all means do.

Also, making it easy for your users to report possible issues also helps lessen the time it takes to get a fix in place should it be something you can work around.