One thing that can fix problems with file type registrations is to rebuild the launch services database.

Have a look at http://www.tuaw.com/2009/06/11/terminal-tips-rebuild-your-launch-services-database-to-clean-up/ on how to do this.

This is just a shot in the dark, but might be worth a try.

Mich würde ja interessieren, ob es auf einem anderen Mac geht. Oder ist das der einzige verfügbare Rechner?

Das wäre meine nächste Frage gewesen. Eigentlich müsste es bei TextEdit auch passieren, da diese App auch NSDocument-basiert ist und in der Sandbox läuft.

Ich habe auch Espresso und Coda (und viele weitere Editoren) auf meinem Rechner, aber habe das Problem nicht. Leider gehen mir die Ideen aus, an was es liegen könnte :(

Textastic uses the value "Owner" for the "LSHandlerRank" key for HTML documents in its info.plist.

I assume that launch services randomly chooses one of the "Owner" apps for each file type to be the default app.

But, Safari has the key "LSIsAppleDefaultForType" set to true which should probably rank higher.

This is what the docs say:

LSHandlerRank: Determines how Launch Services ranks this app among the apps that declare themselves editors or viewers of files of this type. The possible values are: Owner (this app is the creator of files of this type), Alternate (this app is a secondary viewer of files of this type), None (this app must never be used to open files of this type, but it accepts drops of files of this type), Default (default; this app doesn’t accept drops of files of this type). Launch Services uses the value ofLSHandlerRank to determine the app to use to open files of this type. The order of precedence is: Owner, Alternate, None.

Since Textastic is a creator of html files, I chose "Owner" and not "Alternate".

I guess changing it to "Alternate" would leave Safari the default in all cases.

So Mac OS X automatically chose Textastic as the default and you didn't select it in the "Get Info" dialog in Finder?

It doesn't do that on my machines - Safari is still the default. I'd have to explicitly tell the OS to use Textastic "to open all documents like this one".

Is this on Mountain Lion?