HTMLEditor is for typing html code only. You could use the <style> and <script> tags to code CSS and Javascript.
HTMLEditor files must have a ".code" extension. If you don't type the extension in the code name, the extension will come by itself.
All the codes you save are saved in a localStorage item called "HEcodes". Please don't use functions like localStorage.setItem("HEcodes"), localStorage.removeItem("HEcodes"), or localStorage.clear().
While uploading codes, please try to upload only html or txt files.