[SOLVED] Kate Error Message

[JoHubb]

Every time I open a particular file in Kate I get this:

The file /home/../../..xxx.html was opened with UTF-8 encoding but contained invalid characters.
It is set to read-only mode, as saving might destroy its content.
Either reopen the file with the correct encoding chosen or enable the read-write mode again in the tools menu to be able to edit it.

I have successively removed lines of html text in the document to try to isolate an invalid character but even with one line, this error message appears.
The UTF-8 encoding is the same across all my html files and the others all open without this error message.

I have checked all the other controls and as far as I can see these are identical for all my html files.

I'd be grateful for advice.

[JoHubb]

I think I fixed this although exactly how, I do not know.

For those interested, I opened the problem .html file with TEA. It showed a line of white squares at the start of a new paragraph. It also showed a block of white squares at the end of the document.
I didn't see these in Kate.

When these were deleted, the file opened without the error message in both TEA, and Kate.

It remains to be seen if this fixes the problem permanently.

[Snowhog]

In what program was the file originally created/saved in?

[JoHubb]

In what program was the file originally created/saved in?

I wrote directly in Kate and saved as .html. No pasting/copying from anywhere. That's what bothered me. AFAIK I did nothing different with this file than with dozens of others.

Funny thing was that once I enabled 'Read-Write' I could add to the document. But when I tried to copy/paste the new text to material already on the destination page, nothing pasted.

It transfers now just as usual.