I'm not sure what you actually mean - since I don't know what a RS3 HTML5 Client is - but if you are looking for RS3 HTML codes then click on this thread: https://www.rune-server.ee/programmi...000-files.html
You can find them down below.
PS: You posted it in the wrong section Next time post here: https://www.rune-server.ee/runescape...t-server/help/ or here: https://www.rune-server.ee/programmi...elopment/help/