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Yes, I just copied and pasted your code into a new HTML file. I am using the same iOS version and the latest version of Textastic. 

Then I pressed the preview/glasses button. 
The example works on my iPad. Just ignore the "ubiquitouspreview://null" title - it's a result of how the preview in Textastic works.

Here is a screenshot of the alert:



There isn't currently a built-in preview, but you can just drag the file icon from Textastic's window title bar onto your browser's Dock icon. This will open the file in the browser.
You can do that with Textastic's Find & Replace feature.

Click on the loupe icon in the find field, choose "Insert Pattern" and "Line Break". Do the same again to add another line break to the find field.

Then click on the replace field and choose "Insert Pattern" and "Line Break" again from the find field menu to add a line break to the replace field.

It should then look like this:



When you press the "All" button it should replace all double line breaks with one line break.
Hello,

Textastic does not add lines to an existing file when it is opened. I guess that the blank lines actually exist in the file.

What happens when you open the file in another editor (like Apple's TextEdit)? 

If the lines really only show up in Textastic and not in another app, it would be great if you could send me such a file so that I can have a look at it.

You can bring up Find & Replace with Edit -> Find -> Find and Replace or the Cmd-Alt-F keyboard shortcut.
Automatically generating tags sounds like an interesting idea though!
If you press the Ctrl key after the drag starts, the green "+" next to the cursor will change to a small "link" icon. This changes the behavior so that the path is added instead of the files contents.

This is standard Mac Drag & Drop behavior.
You can find instructions for installing the Swift syntax definition in the iOS apps here:

http://feedback.textasticapp.com/topic/454769-swif...

I plan to add it in the next update, but for now you can install it manually.
Hello,

if you are using the full version from the Mac App Store (not the trial version), you should see an iCloud tab in the open dialog (File -> Open) that contains all your iCloud documents.