I worked for a medical software company which had to deal with incoming digital images (DICOM) from all kinds of manufacturers (Siemens, GE, Philips, and tons o

I worked for a medical software company which had to deal with incoming digital images (DICOM) from all kinds of manufacturers (Siemens, GE, Philips, and tons of other smaller players). I once heard one of our lead developers say that 80% of the code we wrote was to work around problems in everyone else's implementations. The DICOM format has a bunch of predefined fields and supports custom fields that manufacturers can use, but a lot of manufacturers would, for no reason I could figure out, use fields incorrectly a surprising amount of the time. They would store one of the most basic pieces of information in the wrong field, and then store that data nowhere, or put it in a custom field, or store it in the wrong format, etc. Enough manufacturers doing 95% of things right and 5% of things wrong, making everyone else jump through hoops to handle their broken behaviour, and suddenly your code grows massively. Sure enough, we had to write an entire system for remapping fields from certain machines so that incoming data from broken implementations would be somehow magically coerced into being correct (either by simply copying data over to fields, or more advanced post-processing). The less time browsers spend wondering what to do with inherently, irredeemably broken HTML, the faster they can render content which actually does work properly. Unfortunately, that only works in controlled environments, like store kiosks, intranets, etc. Otherwise you end up choking on the 95% of the content which is only 5% broken.