Let's say you have a project for an ESP with a number of webpages, stylesheets and images.
Normaly you would do thinks like that:
const char settingspage PROGMEM = "This is my settingspage" ;
const char defaultpage PROGMEM = R"===(This is my defaultpage")==="; // This is the easier way to pass large strings to an array
If you're developing many projects with an ESP8266, it would be usefull that you can configure your ESP (e.g. IP Address) via Browser.
I've developed a convinient way, based on the WebServerExample at https://github.com/esp8266/Arduino.