Why Opera’s XHTML Error Handling Is Superior

I found this old, unfinished post in my drafts. I’m not quite sure when I originally wrote it, but it was over a year ago. Rather than updating the content I decided to publish it as is, as I’m not sure why I didn’t, with a small addendum at the end.


I made a little compilation of the various error messages displayed by browsers upon encountering an XML syntax error. Firefox (Gecko) has the unfriendly looking error on top, Chromium (Webkit) renders the page up to the error, but shows a large error message (albeit not at all useful like in Opera & Fx), and for Opera I included 10.10 and the latest 10.50 pre-alpha build. Note that it’s just the styles behind the error message that changed a bit: the content and helpfulness of the error message is still the same. I’ll run it down a bit more:

  • Firefox displays an error message that’s only useful if you already know sufficiently much about X(HT)ML, whereas Opera’s error message not only highlights more clearly where parsing failed — although ultimately this difference might just be one of preference. More important, its error message might just helpfully link you precisely where you need to go to learn how to avoid it. When I first started messing about with XHTML back in ’03 or so, I probably would’ve appreciated it if Opera had done that. At the time Opera behaved the same as Fx does now.
  • Chromium displays an error message that doesn’t even manage to clearly indicate what’s the problem. This compares negatively to Fx and Opera highlighting the &.
  • Chromium renders the page up to the problem, which may result in a get out of jail free card. The error message doesn’t seem very annoying, but if the error is in the middle of the page it’ll still be in the way. In my sample page it’s at the end, however. (My example page is basically a standard installation of phpGraphy on which I decided to switch to application/xml+xhtml because it claims to be more or less XHTML compliant now — I had to fix all the unclosed meta and link tags first.)
  • Despite rendering the page, you won’t be able to see the page fully in Chromium. You will with Opera’s reparse as HTML function.

I hope that clarifies why I think Opera’s handling is best, both as a user and as an author.


This blog post is now outdated. You can return to the behavior I hailed by disabling the opera:config#UserPrefs|AutomaticallyreparseXHTMLwithparsingerrorsasHTML option.

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