Problem writing a string to a client


print(const char) doesn't know that your const char is in PROGMEM

use the PROGMEM version of print() by casting the parameter to __FlashStringHelper used by F() macro

client.println((__FlashStringHelper*) StyleHTML);


Thanks for the reply.

Where is __FlashStringHelper used by F() macro documented?

nowhere. it was meant to be a hidden helper. but in case where you don't want to use F() macro but a global PROGMEM string with Print class progmem functions, it is useful to know.

F() macro doc