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Just tap on the editor once with two fingers.

This is currently explained in the Gettings Started file, but not yet in the manual.
Unfortunately, I don't have such a GMX Mediacent or 1&1 Smartdrive account. Would it be possible to send me login details so I can try to reproduce the issue?

If yes, please send the information to support@textasticapp.com.
The tabs in iOS 5 beta 3 are limited to a number of 8 so that they are still touchable. Also, in Safari, most of the time you don't have the on-screen keyboard visible all the time like in Textastic.
You can send the file to support@textasticapp.com
Yup, thanks for letting me know.

I already submitted an update to Apple which was supposed to fix this issue, but it also fixes some other odd behaviour on iOS 5. The update should be available any day now.
Is there any chance you can send me the problematic file by email?
Currently, Textastic only supports monospaced fonts and assumes that all characters have the same width. This is not the case for MS Sans Serif which is a proportional font.

Also, unfortunately, Thai is a very complex script with complex Unicode properties (for example, several indivdual unicode characters can be displayed as one) and this is not supported in the current version of Textastic. I'm currently working on Textastic 3.0 and I might support Thai in that version. This largely depends on if I can make this perform fast enough.