I argued in my last post that implementing IE's <meta> tag for opt-in engine selection puts an extremely heavy burden on browser development in the long term. Furthermore, I just don't see the need for it in Firefox. I meet up with Web developers a few times a year, plus I am exposed to a lot of bug traffic, and I always ask the developers I meet whether they have problems with Firefox breaking their sites. So far I've not met one who rated this as an important issue. I'm not saying we don't, or that site breaking is unimportant; I work very hard to fix reported regressions. I do think our users don't clamour for cast-iron compatibility the way IE users apparently do. There are a few possible reasons:
- Lack of intranet penetration. Anecdotally, intranets are full of unmaintained, hairy Web content. Public sites with lots of users have high traffic and can justify maintenance; no-one cares if unmaintained low traffic sites drop out of site. Not so with intranet sites. Since we have pretty low market share in intranets, we don't see the problems there.
- Setting developer expectations. We have always revved our engine on a regular basis and never promised, nor delivered, total compatibility. Developers understand this and have set their expectations accordingly.
- Better historical adherence to standards. I think it's fair to say that IE's standards-breaking bugs have been a lot more severe historically than ours have, since the Firefox resurrection. So when we fix our bugs to become more standards compliant, that has a much lesser effect on Web sites.
What's remarkable is that we've not been hit by compatibility concerns even though up to and including our latest shipping product, we had no serious test automation! Thanks to all the test automation work during the Firefox 3 cycle, we should be even better at compatibility in the future.
It seems clear that for now we have no market need for drastic multi-engine compatibility, and therefore there's no need to even consider the pain it would cause. One could argue that by slaving themselves to the needs of the corporate intranet, IE is actually being hobbled for the mass market.
People have raised the "archival format" issue ... how do archaeologists decipher the late-90s Web far in the future. I honestly think that for total compatibility the best approach is virtual machines running the software of the age. As I mentioned in my last post, even the best side-by-side-engine efforts can't actually guarantee total compatibility. I don't think this should be a goal for Firefox. Maybe if there was nothing else left to do...