Hi

I'm using the current version of the Free HTML Editor on Windows 7 64 bit and am starting the program as administrator.

Does the paid version of the HTML Editor have color coded opening <tag> and closing </tag> matching similar to Notepad ++?

Of secondary concern - Why am I getting an error about 'content type is application/octet-stream' when I attempt to use the built-in validator? The HMTL validates when I upload the files manually.

To your first question: The free and the paid versions have the same colouring.

To your second question: Not sure. Are you saving any changes before you try validating?

Tag matching must not be an option, then. I saw that it wasn't a couple of years ago but was hoping things had changed.

Regarding my second question - Yes.

Regarding that error message, your best bet is to open a support ticket.
You can download a trial copy of the paid version, it has the same functions after you pay, only the trial version is limited to 3 weeks or so.