w3c validation UTF-8 encoding error

With w3c validator you could get this error:
«Sorry, I am unable to validate this document because on line 3400 it contained one or more bytes that I cannot interpret as utf-8 (in other words, the bytes found are not valid values in the specified Character Encoding). Please check both the content of the file and the character encoding indication.» 
That could be because you have some files included in the php file checked by w3c validator, like an .inc one, not encodeed as UTF-8.
To fix this oproblem you have to encode all the components of a php file as UTF-8.

batch change encoding to UTF-8 for several text (php) files

You can use recode
recode UTF-8 *.php -v

provided that all the files have the same encoding.
Otherwise you can try with something like
iconv -f US-ASCII -t UTF-8 *.php

a minor problem

It could be an apparent problem if there aren’t non-ascii characters in a file: then these files are yet recognized, with
file -i --mime-encoding *
as us-ascii.
So you can add a non ascii character, like è:
sed -i -e “$aè” *.php

and afterwards redo the command “recode” as above and replace some ascii expression, like agrave; with UFT-8 à character.
Eventually you will delete the “è” from the end of the files.

How to change encodig of “.srt” Subtitle File in UTF-8

To encode your SRT file in UTF-8 (for instance: “video.srt”), please follow this process:

1. Rename (F2) the “video.srt” file with your PC in “video.srt.txt”.
2. Launch a text app, like Kate.
3. Click on the “File” menu then select “Save the file as…”.
4. In coding option, select “UTF-8”. Then save your file.
5. Rename (F2) the file “video.srt.txt” to “video.srt”.
Done!

from: Zappiti Player 4K [EN]

“travasare” del testo greco antico da fonte UTF-8

Si trovano su internet testi in greco antico resi con unicode (UTF-8). Per salvarli sul proprio PC non è detto che basti un copia e incolla: bisogna vedere dove si incolla. Abbiamo provato, senza successo, con Quanta e con RJ-Texted. Invece siamo riusciti con Kompozer: ha incollato giusto il testo al primo colpo. Non solo, ma è stato facile anche togliere tutti i fatidiosissimi link posti da Perseus, e togliere poi, con pochi clic anche tutta la formattazione, per avere così un testo perfettamente pulito (in UTF-8).