First of all, 1% of a large number is still a large number. A 1% increase in users is not usually something to be sniffed at.
For Buzzfeed, for example, 1% of visits is actually 13 million requests per month.
For example, Sky Broadband once accidentally blocked Jquery which caused lots of sites to break. And this is another one I’ve experienced myself—when I worked at T-Mobile they blocked certain scripts to improve performance.
(And that’s just one of the problems that I noted in my discussion of single page applications.)
What to do about it
So the first thing to do is follow Tim Berners-Lee’s rule of least power by doing as much work further down the stack as we can.
The answer to that is around 1% of the time.
If you had an application bug which occurred 1% of the time, you’d fix it. No team I’ve come across would put up with that level of reliability.
When it fails, it’s our job to make sure we don’t exclude users from accessing the products we make by designing resilient interfaces.
Thanks a lot to Caroline Jarrett for her feedback and suggestions.
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