By Simon Willison

HTCs and Service Pack 2

By Simon Willison

I haven’t played with XP Service Pack 2 yet due to not having ready access to a Windows smachine that I can upgrade, but it seems that one of the security changes made to IE has greatly increased the importance of serving up the correct Content-Type header. Aldo Hoebon writes about this in HTC components in XP Service Pack 2, and describes how the wrong Content-Type for a proprietary IE HTC file (as seen in the alpha-transparent PNG fix for that browser) can cause the HTC file to have no effect.

  • Nice one, never knew that. HTC is not really standard anyhow, so thats not too much of a problem:)

  • Anne

    It’s important however, since HTCs are used for the IE7 project, to name a famous example.

  • Peej

    Yeah leaned all about this the hard way. Problem is that IIS on SP2’d systems or on Win2k3 will not serve files it doesn’t recognise.
    We had this with .VBD files (the old way of running VB apps inside IE)you need to add a mime type for the file you wish to serve ( and in some cases you need to reboot the server)or you’ll get a 404 error…

    Theres info on this at

  • Just because that the IE7 project uses it doesn’t really make it important. If you want fabulous designs, and want to make the design world a better place, stick with standards.

  • Ben Curtis

    I think webgodjj may be thinking of Microsoft’s next IE — the IE7 project ( is specifically useful because it allows you to code to standards and still get IE5+ to recognize your code. Without IE7, I’d have all sorts of CSS hacks throughout my stylesheets in order to make IE comply. CSS hacks may seem like standards, but until they standardize the bugs the hacks rely on I try to stay away.

  • Jed Watson

    I’m as big a pusher of standards (and firefox ;-) as they come, but in a commercial situation where you’ve got a CMS built for IE6 only, written mostly with .HTC files, this WAS really important. For some of us it’s got to do with money and functionality, not design. In my opinion Microsoft stuffed up by burning the very people they enticed into their new technology years ago.

    So thanks a lot for the info – much appreciated.

  • Dean Edwards

    IE7 no longer uses HTCs. It is now a pure JavaScript solution. Some developers did not have access to their servers and could not make the necessary configurations there.

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